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Full text of "The geology of the Cromwell subdivision, western Otago division"

.-J 



Digitized by the Internet Archive 

in 2013 



http://archive.org/details/geologyofcromwelOOpark 




Photo lent by J. Ho^val■d Jackson, General Manager, 



Blue Spur Claim, Gabriel's Gully, Lawrence, N.Z. 
Showing Smooth, Slickeiisided Fault-plane that has been uncovered by Removal of Gold-drift for a Vertical Depth of nearly 000 ft. 



Pepartirtenf /to. 




of "2{ltnes. 



NEW ZEALAND GEOLOGICAL SURVEY. 

(J. M. BELL, Director.) 



BULLETIN No. 5 (NEW SERIES). 



THE GEOLOGY 



CROMWELL SUBDIVISION, 

WESTERN OTAGO DIVISION. 



JAMES PARK, M.Inst.M. and M. (London), M.A.Inst.M.E., F.G.S. (London), 
Director of the Ot.\oo University School ok Mines, Professor of Mining and Mining 

Geology in thf. University of Otago. 



ISSUED UNDER THE AUTHORITY OF THE HON. .JAMES .McGOWAN. MI.MSTEK OK MINES 




NEW ZEALAND. 
BY AUTHORITY: .JOHN MACKAY, GOVERNMENT PRINTER, WELLINGTON. 

1908. 



Ill 



LETTEE OF TRANSMITTAL. 



Geolochcai. Sukvky Offick, 

Wellington, 21st November, 1907. 



SlR,- 



1 have the honour to submit herewith in galley-forni Bulletin 
No. 5 (new series) of the New Zealand Geological Survey. 

It contains the results of the work accomplished by Professor James 
Park, Director of the Otago University School of Mines, in the Cromwell 
Subdivision of Western Otago, during the field season of 1906-7. 

The Bulletin is accompanied by ten maps and six sheets of sections, 
and is illustrated by numerous plates and figures. 



I have the honour to be, 
Sir, 
Your obedient servant, 

J. M. BELL, 
Director, Geological Survey, 



Hon. James McGowan, 

Minister of ]Mines, 

Wellington. 



CONTENTS. 



Letter of Transmittal 



Page 
iii 



Chapter I. — General Information. 



General Description of District 
Scope of Work 
Acknowledgments 



Page 
1 



General Geological Features 
Previous (Jeological Work 



Otago Peneplain 

Origin of Peneplains 

Age of Otago Peneplain 

Origin of Otago Peneplain 
Block Mountains 

The D\mstan Base-level of Erosion 
Dunstan Range 
Pisa Range 
t'arrick Range 
Remarkable Mountains 
Rock Pillars and Knobs 
(Jenesis of Pisa and Carrick Hornts 
Systematic Investigation of Block Mountains 
Cromwell Basin 



Chapter II. — Phtsiography. 
t) Cromwell Basin 



continued. 

Origin of Cromwell Basin 

History of Cromwell Ba.sin 
Deformed Lake-basins . . 

The Roaring Meg Coal- basin . . 

The Oibbston Coal- basin 

Origin of Deformed Lake-baoiuti 
Valleys of »osion 

Dunstan Gorge 

Kawarau Gorge 
Lakes and Mountain-tams 
Rivers 
Climat* 
Vegetation 



ir. 

17 
lit 
1!» 
19 
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20 
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23 
23 



Chapter 



Table of Formations 
Maniototo Series 

Distribution 

Rocks 

Disposition of Strata 

Foliation 

Thickness 

Origin of Schists 

Dynamical Origin of Metamorph'sni 

Relation to Underlying Formation 

Age 

Eruptive Rocks 

Economic Minerals 
Kakanui Series 

Distribution 

Rocks 





. 24 




. 24 




24 




24 




. 26 




25 




25 




25 1 




. 25 




. 27 i 




28 1 




28 




2!) 




30 




. 30 1 




30 1 



III.— Gkneral Geology. 

Kakanui Series — continued. 

Thickness 

Relation to Underlying Formation 

Relation to Overlj-ing Formation 

Age 

Eruptive Rocks 

Economic Minerals 
Pliocene (Lacustrine Series) 

Cromwell Section 

Bannockbum Section 
28 < Pleistocene 

Morainic Matter 

High-level Gravels 

.Modified (ilacier Drift 

Terrace Gravels 
Recent 



30 
3(J 
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31 
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35 



Chapter IV.- 
Some Principles of Concentration in River-bed 
(iiavels 
Progress of River Erosion 
River-bed Bottom 
Position of Pay-wash 

Descent and Arrest of Gold in Travelling Drift 
Alluvial Gold 
Quartz Drifts 



-Economic Gkulugy. ' 

Alluvial (Jold — continued. 

36 ; Sandstone Gravels 

3B t Fluviatile Drifts forming Terraces 

37 [ Leads at Quartz Reef Point . . 

37 Fluvio-glacial Deposits and Moraines 
30 Re-sorted Fluvio-glacial Drift 

40 I River-bed Gravels and Sands 

41 I Crumbling Schist Wash 





42 




42 




43 




44 




45 




46 




40 



VI 



Chapter IV. 



The Blowing-down System of Sluicing 
Scope of System 
The Actual Working 
Gold-bearing Lodes 
Bendigo Goldfield 
Situation 
Access . . 
Discovery 
Rocks . . 
Vein-systems 
Cross-lodes 

The Cross-lode . . 
East and West Lodes 
North Lode 
Cromwell Lode . . 
The South Lode . . 
The Bee Lode . . 
Hit or Miss Lode 
Aurora Lode 
Anderson's Lode 
Luckiiow Lode . . 
Bradford's Lode . . 
Low-level Adit . . 
Alta Lode 
Rise and Shine Impregnated Shear Zone 
Genesis of (jold in Shear Zone 
Carrick Goldfield 
Situation 
Discovery 
Rocks . . 
Vein-systems 
Carrick Gold-bearing Lodes 
New Royal Standard No. 1 
New Royal Standard No. 2 
Crown and Cross Lode 
New Find Lode . . 
Caledonia Lode . . 
New Caledonia Lode 



-Economic 
Page 



GKor.oGY — continued. 



47 
47 
47 
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55 
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37 
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60 
60 



Gold-bearing Lodes — continued. 
Carrick Goldfield— conh'««erf. 
Carricktown Lodes 
Elizabeth Lode . . 
Colleen Bawn Lode 
Star of the East Lode 
The Old Heart of Oak Lode 
Black Horse Lode 
Pipeclay GuUj' Lodes 
John Bull Lode 
Robert Biuns Lode 
Golden Gate Lode 
Genesis of Bendigo and Carrick Lodes 
Immature Replacement Lodes 
Origin of Minerals 
Age of Lodes 
Position of Pay -ore 
Secondary Enrichment 
Hawksbiu^ Lode 
John Bull Quartz Veins 
Lodes in Basin of Roaring !Meg 
Henderon's Lode . . 
Roaring Meg Veins 
Silver 
Antimony 

Buchan's Lode.s 
Horn's Lode 
Asbestos 
Graphite 
Coal . . 

Excelsior Coal-mine . . 
Shepherd's Creek Coal-mine 
Roaring Meg Coal 
Gibbston Coal-mine . . 
Cardrona Coal-mine . . 
Artesian Water in Central Otago 



Page 

61 
61 
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62 
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Metamorphic Rocks 

Epidotized Chlorite-schist 

Quartz-chlorite-schist, with Epidote 

Micaceous Quartz-schist 

Chloritic Quartz-schist 

Micaceous Quartz-schist 

Granular Chlorite-schist 

Schistose Greywacke 

Mica-schist . . 

Altered Greywacke 

Serpentine . . , 
Detrital Igneous Rocks 

Hypersthene-diorite . . 
- Peldspar-porphyrite . . 

Mica -gneiss . . 



Chapt 


ER V. — ' 


.. 751 




. 75 




75 




. 76 




. 76 




. 76 




. 77 




. 78 




. 78 




. 78 




. 79 




.. 80 




. 80 




. 80 




. 81 ' 



Petrography. 

Detrital Igneous Rocks — contimied. 
Biotite-granite 
Augite-hypersthene-diorite 
Augite-mica-diorite . . 
Hornblende-schist 
Hornblende-diorite 
Hornblende-camptonite 
Pink Quartz-sclust 
Detrital Sedimentary Rocks 
Greywacke . . 
Greywacke . . 
Greywacke . . 
Greywacke . . 
Sandstone 



81 

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84 
84 
84 
85 



Vll 



LIST OF ILLUSTRATIONS ACCOMPANYING BULLETIN No. 5. 



Plate 

I, 
II 



Blue Spur Claim, Gabriel's Gully, Lawrence 

Obelisk on Old Man Bangs : A typical rock-pillar 

Double Cc>ne, north end of Remarkables, from head of Doolan's Creek . . . . ) 

Double Cone, north end of Remarkables, showing Lake Alia Cirque, taken from Mount 
Kamsay, 7,100ft. .. .. .. .. .. ..) 

III. Lake Alta, 6,050 ft., at foot of Double Cone, Reraarkablts . . 

IV. Roaring Meg, at mouth .. .. .. .. .. .. ..[ 

Roaring Meg, above Henderfeon '8 .. .. .. ..) 

V. Boulder showing a faulted vein of quartz that has been puckered while the enclosing altered 
grejwacke has been compressed .. 

VI. Mouth of Shepherd's Creek. Bannockburn, showing tilted ends of Laouetrine Series 

VII. 



Faclug page 
Frontispiece. 

12 



VIII. 

IX. 

X. 
XI. 

XII. 

XIII. 
XIV. 
XV. 
XVI. 



Mouth of Kawarau Gorge, taken from summit of moraino. . 
Mouth of Kawarau Gorge, Cromwell . . 

Kawarau Moraine, Cromwell 

Ice-shorn rock near Kawarau Bridge, Gibbston . . 



Lowburn Valley, near pource, showing Pisa Range in biickground 

Showing " blowing-down " system cf working alluvial jrcurd, Lowburn, Central Otsgo 

Lowburn Terraces, from Deadman's Point, Cromwell 

Bendigo Mine, near Cromwell, Clulba Vallty 



Caledonia Mine, Carrick Range 
Geological Survey camp, Cromwell 

Junction of Clutba and Kawarau Rivets, Cromwell 

Clutba Valley, opposite Bendigo 

Bannockburn, and Clu'ha Valley 

1. Kpidotized cblorite-scbist, eastern flnuks Pisa Range 

2. Cliloritic quartz schist from Carrick Range .. 

3. Granular chlorite-schist, Gibbston 

4. Mica-Echist, Cromwell.. 

XVII. 1. Serjentine from Sj ringburn, near Mf nnt Hocken 
2. Hyp< rsthcnedioiite, Kawarau gravels 
.3. Felds^par porphvritc, Kawarau gravels 
i. Mica-gneifs, Kawarau gta\elf< 

XVIII. 1. Biotitegranite, Kawarau gravels . . 

2. Augite-b^ per.Mbenediorite, Kawarau gravels 

3. Augite-dioritc, Kauwarflu gravels. . 

4. Hornblende-pchist, Kawarau gravels 

XIX. 1. Hornblende-caniptonitp, from terrace near Becdigo Goldfield 

2. Mica-schist, Double Cone, Remarkables 

3. Mioa-soh)8t, Bendigo Goldfields 

XX. 1. Schistose gre\ wacke, from flanks of Carrick Range 

2. Greywacke, Kawarau gravels 

3. Altered greywacke. Double Cone . . 

4. Greywacke, Kawarau gravels 



::1 



12 

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22 

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40 

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48 

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62 

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79 

81 
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Vlll 



MAPS ACCOMPANYING BULLETIN No. o. 



1. New Zealand, showing land districts and divisions 

2. Western Otago Division, showing survey districts 

3. Geological map of Wakefield Survey District . . 

4. Geological map of Cromwell Survey District . . 

5. Topographical map of north end of the Remarkables 

6. Geological map of Kawarau and Crown Survey Districts. . 

7. Geological map of part of Cromwell Township 

8. Plan of the Cromwell Gold Company's mining property, Bendigo 

9. Geological map of Bannockburn Survey District 

10. Geolrgical map of Bannockburn Coalfields aud Carriok Goldfield 



Facing pag« 
viii 

viii 

10 

18 

21 

26 

46 

56 

58 

70 



GEOLOGICAL SECTIONS ACCOMPANYING BULLETIN No. o. 



1. Section along line AB, Wakefield Survey District 
Section along line A A, Cromwell Survey District 
Section along line BB, Cromwell Survey District 
Section along line A.-i, Kawarau Survey District 
Section along line AA, Bannockburn Survey District 
Section along line BB, Crown and Kawarau Survey Districts 

2. Section along tail-race nf ar Chinese Camp, Cromwell 

3. Section across lake-beds at Quartzvilie, Smith's Gully 
Section across lake-beds near Pipeclay Gully . . 

4. Section across lake-beds on the western flank of Round Hill 
Section across lake beds near long gully 

5. Section across lake-beds at entrance of Kawarau Gorge 

6. Section along line AA, Bannockburn Coalfields . . . 
Section along line BB, Bannockburn Coalfields 



Facing pags 
30 

32 

34 

34 
34 
72 




By Auiheriiy : John .Vackay, Govemmtnt Pnnltr. 



BULLETIN No. 5 (NEW SEEIES). 



THE GEOLOGY 



7 



OF THE 



CKOMWELL SUBDIVISION, 



WESTERN OTAGO DIVISION. 



CHAPTER L 



GENERAL INFORMATION. 



General Description of District 
Scope of Work 
Acknowledgments 



Page 
1 
2 
3 



General Geological Features 
Previous Geological Work 



rage 
3 
3 



General Description of District. 



The area dealt with in this report extends from Bendigo to Cromwell, and from Cromwell to Bannock- 
burn, and thence along the valley of the Kawarau to Gibbston, Double Cone, Crowii Terrace, and 
the headwaters of Soho Creek. It includes the west side of the Duustan Mountains, the south- 
west half of Pisa Range, the north-east side of Carrick Range, and the north end of the Remarkables, 
embracing \vithin its limits the Survey Districts of Wakefield, Cromwell, Bannockburn, Crown, and 
Kawarau, in the Otago Land District. 

Cromwell, with some six hundred inhabitants, is the county town and chief centre of population 
in the district. It is situated on the river-terrace at the junction of the Clutha and Kawarau Rivers. 
The only other centre of population is the mining township of Bamiockburn, situated on the south side 
of the Kawarau, about three miles distant from Cromwell. 

The Cromwell Flat, extends from the Clutha and Kawarau, back to the foot of Pisa Range. It 
comprises an area of some 4,000 or 5,000 acres of light but rich land that cannot be brought under 
cultivation without irrigation. 

Behind the flat and extending along the foothills from the Kawarau Gorge to the upper part of the 
Lowburn there is a string of prosperous irrigation farms. The soil in this strip is not richer than on the 
flat land below, but its situation is such that it is easily irrigated by the streams descending from Pisa 
Range. 

The valleys, with the exception of the Cromwell basin, are in most places narrow, the majority 
being little better than steep gorges or rocln- defiles. 

The surface of the land is commonly steep, often precipitous, rising rapidly from the floor of the 
valleys, mostly under 1,000 ft. above sea-level, to the crests of the encircling mountains, or to the edge 
of the mountain plateaux, which attain heights ranging from 4,000 ft. to 7,600 ft. 
1 — Cromwell. 



The suiumits of the Dunstan Mountains and Carrick and Pisa Ranges are remnants of the great 
elevated base-level plain of erosion of Central and Eastern Otago, and, as such, are flat or gently undulat- 
ing. They are excellent high lands for the pasturage of sheep in spring, summer, and autumn, being 
well covered with native grasses and other subalpine vegetation. 

On the other hand, the slopes leading up from the low country to the mountain-tops are commonly 
steep, rugged, and broken, being often occupied by conspicuous stretches of brown craggy rock, in the 
hollows of which a scanty growth of native and imported plants struggles for a bare existence. 

These steep slopes, whether those of valley, gorge, or defile, with their tumbled, fissured rock forming 
innumerable places of shelter and refuge, are the home and breeding-place of the rabbit, which is the 
scourge of the sheep-farmer throughout Central Otago. 

This region lies in the dry belt of Western Otago. The high snow-covered ranges to the westward, 
forming the axis of the main mountain-system of Otago, intercept the moisture-laden ^\dnds from the 
Pacific, which, lea\'ing their moisture behind, sweep over this area as excessively dry winds that bring 
no good with them, but only evil, for in their course they dry up the struggling vegetation and lick up 
the remaining moisture from the parched-up land. 

Thus it is that the rainfall is scanty, more especially in the low la)ids and foothills. 

The mountains are often seen to intercept rain-clouds that hang on the tops until exhausted 
of their moisture. The alpine vegetation, under the influence of the warm sunshine, gladly responds to 
the greater rainfall, hence, while the river-flats, terraces, and foothills are bare and thirsty, except where 
irrigated, the mountain lands are covered with good pasture, even in midsummer. For this reason 
no correct judgment of the value of the country for pastoral purposes can be formed from the condition 
of the pasturage along the road routes, which in most cases follow the floor of the river- valleys. 

The country in its natural state is quite destitute of trees and all forest vegetation. 



Scope of the Work. 

The work undertaken during the summer of 1906-7 included an examination of the physical features 
and surface-forms of the district, of the geological structure, of former glaciation, of the nature and extent 
of the gold-bearing drifts, coal-deposits, and metalhferous lodes, of the soil, and water-supply. With 
respect to the latter, special attention was directed to the collection of data bearing on the probable 
existence of artesian water in the old lake-basins of Central Otago. 

A special examination was made of the Bendigo and Carrick Range gold-bearing lodes, and of the 
Bannockburn coalfield ; and enlarged maps of these areas will be found accompanying the detailed 
description in Chapter IV, devoted to economic geology. 

The topography on the geological maps is based on the excellent maps of the Lands and Survey 
Department. Many details not shown on these were filled in by chaining and inspection, where the 
cadastral surveys made this course possible. In other cases special surveys were made by chain and 
prismatic compass. 

On the special maps accompanying the writer's report on the Alexandra Sheet* the reHef of the 
surface was shown by contour-lines fixed by prismatic compass and Abney level. No contours are 
shown on the special maps in this report, as the circumstances did not seem to warrant the great ex- 
penditure of time and labour which this course would have involved. ^ 

Contour-lines afford the only means by which the surface rehef can be shown on paper, and in the 
case of active mining centres it is of the utmost importance that this method should be followed. 

The general maps have been printed on a scale of 1 in. to the mile, and the amount of detail in- 
troduced is what was considered necessary to bring out clearly the distinctive features of the geological 
structure ; but it will be found in all cases that the degree of accuracy is governed by the scale used. 
Thus, on the one-mile maps the minor subdivisions of the lacustrine series have been suppressed so as to 
avoid confusion, and in some cases the superficial deposits have been omitted where they were liable 
to obscure the geological structure or the continuity of the underlying formation. 

^Bulletin No. 2 (New Series), N.Z. Gfeol. Sur. 1906. 



3 

The opportunity to show detail and to define boundaries of rock-formations with an approach 
to exactitude is greatest on the large-scale maps. For this reason the special maps are not, nor are they 
intended to be", simple enlargements of portions of the general maps. 

The sections of the one-mile maps are drawn to natural scale, and on these there is some unavoid- 
able suppression of detail. They are always drawn looking towards the north, north-east, or north- 
west. 

Acknowledgments. 

The writer wishes to place ou ^ecord his appreciation of the efhcient assistance rendered by nis 
three student-assistants — by Mr. A. MoncriefE Finlayson, M.Sc, in petrological, topographical, and 
general geological detail ; by Mr. A. Gordon Macdonald, B.E., in topographical and mapping work ; 
and by Mr. Phihp H. McDouall, in topographical and geological field-work. Acknowledgments are 
also due to Mr. J. Horn, Chairman of the Vincent County Council ; Mr. J. Little, Mayor of Cromwell ; 
and the numerous miners and mine and dredge managers throughout the district, from whom much 
useful information was obtained with respect to old leads and mines not now in operation. 

General Geological Features. 

The prevaiUng rock is mica-schist, which occurs in two distinct series^namely, a lower highly 
altered mica-schist, and an upper, less altered, slaty, mica-schist. 

The lower schists, besides being more altered and plicated, are characterized by the presence of 
great bands of chlorite-schist, which in many places show conspicuous alteration to epidote, especially 
in the lower horizons. 

Bands of chloritic rock are not absent in the upper schists, but they are commonly very thin and 
unimportant. 

The most important geological feature brought out by the present work is the apparent thickening 
of the lower schists from the Dunstan Mouiitains north-westward to the Arrow River. In a distance 
of thirty miles the thickness increases from 12,000 ft. to .30,000 ft. : but to what extent the increase 
is due to greater sedimentation or to over-thrust folding cannot be ascertained until an examination 
has been made of the Shotover and Wakatipu areas. 

It is noticeable that the increasing thickness seems not only to afEect the mica-schist proper, but 
also some of the intercalated bands of chlorite-schist in a corresponding degree. The paLt'OZoic shore- 
line, on which the sediments that afterwards formed the schists accumulated, manifestly lay towards 
the crystalline massif of the fiord-country lying to the west and south-west. 

There is every reason to believe that the mica-schists are altered sedimentaries, and the chlorite- 
schists altered volcanics of contemporary date. 

In Cromwell basin the schists are overlain by a great thickness of fresh-water beds, at the base of 
which there are seams of lignite of great economic value to the district. 

Following the lacustrine series there is a great assemblage of fluviatile and glacier drifts, ranging 
in age from the close of the Pliocene to recent times. All the gravels and glacier-detritus in the district 
are gold-bearing, and most of them have been worked for payable returns. 

Previous Geological Work. 

The first recorded notice of the geology of Central Otago was that of Dr. Charles Forbes,* of H.M.S. 
" Acheron," who, in 1855, in a paper " On the Geology of New Zealand, wth Note on its Carboniferous 
Deposits," mentions that the mountains in the central portion of the province are composed of crys- 
talUne and metamorphic rocks. 

Then followed Dr. W. Lauder Lindsay, who, seven years later, in a lecture given in Dunedin, com- 
pared the mica-schist of Otago -tt-ith the crystalline rocks of the Grampian Mountains in Scotland. 
Lindsay divided the gold-bearing drifts in Central Otago into two series, the older of which included 



* Quart. Jour. GeoL Soc., London, xi, 521. 
1* — Cromwell. 



the lacustrine beds of the old lake-basins. His shrewd prediction that gold- mining was destined to 
become a great source of wealth in Otago has been amply justified by the continuous gold-production 
of the past fort}^ years. 

In 1865 he read a paper on the Tertiary coals of New Zealand before the Royal Society of Edin- 
burgh, ill which he refers to the lacustrine beds of the Manuherikia basin.* 

It is impossible to speak of the geological work of this pioneer geologist without referring to the 
accuracy of his field observations and the soundness of his generalisations. He may justly claim to have 
laid the foundation of the stratigraphy of New Zealand geology. 

Then followed Dr. (afterwards Sir James) Hector, who as Pro\-incial Geologist devoted several 
years to the unravelling of the geological structure of Otago, besides doing much arduous work in 
exploring regions at that time difficult of access and far removed from centres of population. He began 
his geological work in 1862. 

First as Pro^^ncial Geologist for Otago, and afterwards as Government Geologist for New Zealand, 
Sir James Hector published numerous papers and reports dealing particularly ^nth the geology of Otago. 
A discussion of the scope and \-iews contained in these has already been made by the writer in Bulletin 
No. 2 (New Series), and therefore need not be repeated here. It wall be sufficient for the purpose of 
this report simply to enumerate hereunder the papers referred to, for the information of geological 
students and to obtain continuity of reference. 

1. Otago Provincial Gazette, 3rd September, 1862. 

2. Manuscript, geological map, and section of Otago and Southland — map in Otago University 

Museum ; section in Otago University School of INIines. 

3. Jurors' Reports and Awards of the New Zealand Exhibition. Dunedin, 1865, 

4. " On Mining in New Zealand," Trans. N.Z. Inst., vol. ii, 1869, p. 361. 

5. " Clutha and Green Island Coalfields," N.Z. Geol. Sur. Reports of Explorations, 1871-72, p. 165, 

6. " OutUne of New Zealand Geology," 1886. 

Other papers and publications having a more or less direct bearing on the geology of Central Otago, 
and to some of which the writerf drew special attention in discussing the evolution of geological work 
in Otago since 1862, are as follows : — 

1. " On the Geology of the Country between the Lower Clutha and Mataura Rivers." John 

Buchanan, F.L.S. 1868. 

2. " On the Extinct Glaciers of the Middle Island of New Zealand." W. T. L. Travers, Trans. 

N.Z. Inst., vol. \d, 1873, p. 297. 

3. " On the Glacial Action and Terrace Formations of South New Zealand." J. T. Thomsen, 

Trans. N.Z. Inst., vol. vi, 1873, p. 309. 

4. Table of Sedimentary Formations of New Zealand, Geological Magazine, 1874. 

5. " On the Date of the Last Great Glacier Period in New Zealand." Captain Hutton, Trans., 

N.Z. Inst., vol. V, 1872, p. 384. 

6. " On the Formation of Lake Wakatipu." Captain Hutton, Trans. N.Z. Inst., vol. v, 1872, 

p. 394. 

7. " On the Cause of the Former Great Extension of the Glaciers in New Zealand." Captain 

Hutton, Trans. N.Z. Inst., vol. viii, 1875, p. 383. 

8. " Sketch of the Geology of New Zealand." Captain Hutton, Quart. Jour. Geol. Soc, vol. xli, 

p. 191. 

9. " General Geology of New Zealand." Captain Hutton, Nature, vol. xxxi, p. 305. 



The Geologist, vo}. vi, p. 143. t Bulletin No. 2 (New Series), N.Z Geol, Sur,. 1906, p. 3, 



10. " On the Foliated Rocks of Otago." Captain Hutton, Trans. N.Z. Inst., vol. xxiv, 1891 , 

p. 359. 

11. " Geology of Otago." Captain F. W. Hutton and G. H. F. Ulrich, Dunedin, 1875. 

12. " On Whiiie's Reef." James Park. N.Z. Geol. Sur. Reports of Explorations, 1888-89, p. 32. 

13. " On the Auriferous Drift at Bald Hill Flat, near Alexandra, Otago." James Park, loc. cit., 

p. 30. 

14. " On Tinkers Alluvial Gold-diggings, Otago." James Park, loc. cit.. p. 27. 

15. " German Hills Alluvial Gold-diggings, Otago." James Park, loc. cit., p. 24. 

16. " Galloway Alluvial Gold-diggings." James Park, loc. cit., p. 22. 

17. " Ophir District of Otago." James Park, loc. cit., p. 17. 

18. " Antimony Lode," Alexandra, Otago. James Park, loc. cit., p. 33. 

19. Gordon, H. A., Rept. Mining Industry of N.Z., 1890, p. 76 ; and 1891, p. 70. 

20. " Geology of the Waitaki Valley and part of Vincent and Lake Counties." Alex. McKay, 

N.Z. Geol. Sur. Reports of Explorations, 1881, p. 56. 

21. " On the Antimony Lodes of the Carrick Ranges," Vincent County, Otago. Alex. McKay, 

loc. cit.. 1882, p. 80. 

22. " On the Origin of the Old Lake-basins of Otago (Abstract)." Alex. McKay, Trans. N.Z. 

Inst., vol. xvi, p. 550 ; and X.Z. Geol. Sur. Reports of Explorations, 1883-84, p. 76. 

23. " Report on tho Older Auriferous Drifts of Central Otago." Alex. McKay. Government 

Printer, 'Wellington, 1897. P. 46. 

24. " Gold-deposits of New Zealand." Alex. McKay. Government Printer, Wellington, 1903. 

P. 54. 

25. " The Geology of the Area covered by the .\lexandra Sheet," Central Otago Division. 

James Park. Bulletin No. 2 (New Series), N.Z. Geol. Sur. Government Printer, Wel- 
lington, 1906. 



CHAPTER II. 



PHYSIOGRAPHY. 



Central Otago Peneplain 
Origin of Peneplains . . 
The Central Otago Base- level of Erosion 
Age of Central Otago Peneplain 
Origin of Central Otago Peneplain 

Block Mountains 

Dunstan Range 

Pisa Range 

Carrick Range . . 

Remarkable Mountains . . 

Rock Pillars and Knobs . . 

Genesis of Pisa and Carrick Horsts 

Systematic Investigation of Block Jlountains 

Cromwell Basin 



age 
6 


Cromwell Batsin — continued. 


6 


Origin of Cromwell Basin 


6 


History of Cromwell Basin 


7 


Deformed Lake-basins . . 


8 


The Roaring Mee Coal-basin 


9 


The Gibbston Coal-basin 


9 


Origin of Deformed Lake-basins 


11 


Valleys of Erosion 


11 


Dunstan Gorge 


11 


Kawarau Gorge 


12 


Lakes and Mountain-tarns 


12 


Riv^ers 


13 


Climate 


13 


Vegetation 



Page 

15 
17 
19 
19 
19 
20 
20 
20 
21 
21 
22 
23 
23 



Central Otago Peneplain. 



ORIGIN OF peneplains. 



An elevated peneplain may be (a) an uplifted coastal plain ; {h) an iipUfted base-level formed in 
accordance with Po-n-ell's cycle of fiuviatile erosion ; or (c) a desert upland in an arid climate truncated 
by long- continued subaerial erosion in terms of Passarge's postulate. 

In the region Ijdng between TaranaM and Ruahine Range near the south end of the North Island 
of New Zealand, a great series of marine beds of older and newer Pliocene age * extends from the sea 
inland to the Kaimanawa Mountains and to the foot of Ruapehu, the gigantic volcano that stands 
some thirty miles south of Lake Taupo. 

These marine beds form a gently sloping plain, rising from sea-level to a height of 4,000 ft. 
on the flanks of the Kaimanawas, in a distance of some seventy miles. This sloping plain is 
dissected by the Manawatu, Rangitikei, Wangaehu, Turaldna, and Wanganui Rivers, which, with 
their numerous tributaries, run in deep, narrow, tortuous channels, mostly bounded with steep or 
vertical walls. 

In the upland side the dissection is further advanced than nearer the sea ; and along the foot of 
the Kaimanawas there is a broad transverse rift-valley that is drained by the Rangitikei. This trans- 
verse valley has isolated large blocks of the older Pliocene beds at an elevation of over 3,000 ft. 

These faulted blocks, considered by themselves, present all the characteristics of a dissected pene- 
plain that has reached a mature stage of development. But they caimot be disconnected from the 
sloping coastal plain of which they at one time formed a part ; and their origin is quite clear. They 
are, however, not a little significant, since they show that we must not too lightly abandon old formulae. 
For, given a broad coastal plain, tilted by rapid differential uplift on the upland side, dislocated by 
transverse rifts, and subjected for a time to subaerial erosion, either arid or plu\'ial, we should have a 
truncated upland that might very weU be an elevated and dissected base-level of erosion. 

THE CENTRAL OTAGO BASE-LEVEL OF EROSION. 

This is the most conspicuous physiographic feature of Central Otago. Its extent is clearly indi- 
cated by the numerous parallel and transverse table-topped ranges that occupy this region. Its 
upland side extends from the Waitaki River to the Remarkables, whence it spreads out in the form 
of a great fan into eastern and southern Otago. 



* Park : X.Z. Geol. Sur. Reports of Explorations, 1887. 



The ranges enumerated in a preceding paragraph are portions of this ancient base-level of erosion, 
and, except at the gorges cut by the Clutha, Kawarau, and Manuherilda Rivers, they are not altogether 
disconnected. Thus, on the west side of the Clutha, where the dissection of the base-level has not 
advanced so far as elsewhere, it is possible, by making long detours around the sources of the gullies, 
to ride along the flat-topped summits from the Umbrella Mountains to the Old Man Range and thence 
on to the Carrick and Garv'ie Ranges. 

The surface of the base-level does not necessarily coincide with the plane of foliation of the schist, 
although it does so in many notable cases. On the summit of the Garvie, Carrick, Old Man, and Duu- 
stau Ranges the schists are lying practically horizontal, and in these cases the coincidence of the laud- 
surface and foUation-plane is very remarkable. But in the Pisa, Raggedy, and Puketoi Ranges the 
old surface of the base-level has no relation to the disposition of the schist. 

Eastward of the Rock and Pillar Range we have the great Barewood plateau of erosion, dissected 
by the Taieri and its tributaries into numerous narrow gorges and ra\'ines. Over the greater part 
of the plateau, in an area covering hundreds of square miles, the mica-schist lies almost perfectly 
horizontal. 

What relationship exists between the Central Otago and Barewood base-levels has not yet been 
worked out. WTiether they are separate and distinct, belonging to two plains of erosion of different 
ages, or merely the faulted portions of the saifte base-level plain is a problem that can only be solved 
by a close investigation of the countrj' lying east of the Rock and Pillar Range. The writer has passed 
over the Barewood plateau in many places, and from what he has seen he is inclined to favour the view 
that it is the continuation of the Central Otago base-level on the seaward side of the Rock and Pillar 
fault. 

Of the age of this base-level very little is known at present. 

The evidence in Central Otago shows that it existed before the old lake-basins, now filled with 
Pliocene strata, were formed. 

In the Shag and Waitald Valleys it had been excavated into long narrow fiords, the floor and shores 
of which were afterwards filled with the members of the Oamaru Series of Miocene age. 

We have no known marine strata of Eocene age in New Zealand. There is a long break between 
the Upper Cretaceous Waipara Series and the Oamaru Series. Hence the question may be asked, 
Did the Eocene represent a continuous period of terrestrial erosion throughout Otago, during which 
the surface was worn down to a great coastal plain which afterwards became elevated and faulted ? 

Further reference to this matter is made below. 



AGE OF CENTRAL OTAGO PENEPLAIN. 

This peneplain, as we have seen, is dissected by the Kawarau, Dmistan, and Clutha Gorges, and 
by the Cromwell, Manuherilda, Ida Valley, and Maniototo basins. The former are narrow rift-valleys 
that have been excavated by the combuied action of present-day rivers and ancient glaciers. The 
basins are graben, or faulted depressions, that occupy about 45 per cent, of the original area of the pene- 
plain, and in which there was deposited a pile of fresh -water deposits, in places over 1,000 ft. thick 
The period of deposition probably covered the whole of the Pliocene. 

The surface of the peneplain is covered in places with a thin sheet of small quartz gravel, which 
is rounded or subangular, and often scattered through the loamy peaty soil that covers the greater 
part of the surface. 

The presence of thin beds of marine shells at the foot of Mount Ida, near Naseby, and along the 
foot of the Hawkdun Range, opposite Hill's Creek, shows that the sea had access to the Maniototo. 
basin, the most eastern of the graben, some time about the close of the Miocene or beginning of the 
Pliocene. 

What we do know with certainty is this : A great elevated peneplain that had reached an advanced 
stage of maturity some time prior to the Pliocene, with a surface that was nearly level, commonly inde- 
pendent of the rock-structure, and mostly bare or covered with a thin veneer of quartz gravel, occupied 
the whole of Central Otago prior to the Phocene. 



8 

ORIGIN OF CENTRAL OTAGO PENEPLAIN. 

The great deformed peneplain of Central Otago, of which the group of block mountains formed 
a part, was first noted by the author in 1888 ; and, in conformity with the \dew8 then commonly held 
by physiographers, he regarded it as a remarkably fine example of an elevated and dissected plain of 
marine erosion. 

This conclusion he subsequently abandoned on reading the brilliant definition of Powell's law 
of base-levelling formulated by Professor Davis ; and in a paper on " Some Principles of Flu\T.atile 
Erosion in Relation to Base-levelling,"* summarising the generalisations of Da\'is, with illustrative 
examples dra^vn from New Zealand, he ventured to express the opinion that the truncated highland of 
Otago represented an uplifted base-level of considerable antiquity. 

After the detailed examination of the Alexandra district in 1905-6, the author announced the 
discovery in that region of a group of wonderfully preserved block momitains, which he described as 
remnants of a great peneplain.! But while discussing the origin of the block mountains, he refrained 
from a reference to the origin of the peneplain, as he did not consider that he had gathered sufficient 
evidence to warrant a definite expression of opinion on that point. 

After a detailed examination of the Cromwell district in 1906-7, and a partial re-examination 
of the Alexandra district, the author still finds that the available evidence is scant and inconclusive. 
For his acquaintance with the generalisations of Passarge, first formulated in that writer's book, " Die 
Kalahari" (Berlin, 1904), and elaborated in his papers " RumpfQache mid Inselberge," Zeitschriftder 
deutschengeologischenGesdlschaft,vo[. hi (1904), Protokol, pp. 193-209 ; and " Die Inselberglandschaften 
im tropischen Afrika," Xaturwiss. Wochenschr. (New Series), vol. iii (1904). pp. 657-65, the author is 
specially indebted to Professor Davis's papers on " Levelling without Base-levelling," Science, N.S., 
vol. xxi, May 26, 1905, pp. 825-28 ; " The Geographical Cycle in an Arid Climate," Journal of Geology, 
vol. sdii, July, August, 1905 ; and " Observations in South Africa," Bulletin of the Geological Society 
of America, vol. xvii, pp. 377-450, August, 1906. 

The Central Otago peneplain is either an uplifted base-level of erosion, or an upland desert-plain 
formed in an arid zone. If the former, it seems difficult to conceive that an extensive ocean base- 
level that had attained a stage of extreme maturity could have been uplifted through a vertical 
height of some 5,000 ft. without warping having taken place. Of such warping there is now no 
o\'idence ; but it may be with good warrant contended that the warping took place so long ago that 
subaerial erosion in this arid, wind-swept zone has once more planed the surface down. 

If, again, this is an uplifted base-level, there should exist evidence of an uplifted marginal sea- 
floor, around the new upland, since an elevated base-level must be accompanied by an uplifted sea-floor. 

Such marginal marine deposits do exist. The Oamaru Serits, of probably Lower IVIiocene age, 
consisting of conglomerates and grits, with brown coal, followed by marine clays, greensands, and 
coralhne limestones, thus forming a complete cycle of deposition, was shown by the author in 1904, 
in a paper on " The Marine Tertiaries of Otago and South Canterbury,"! to occur as marginal deposits 
in Southland, eastern Otago, and south Canterbury, resting in many places on the flanks of the uplands 
bordering the Otago peneplain at a height of 2,000 ft. above the sea. 

The other alternative postulates that the Central Otago peneplain is a desert- plain that was 
formed in an arid climate. The ability of long-continued subaerial erosion to truncate an upland to a 
surface of low relief, or even to a plain, has long been recognised. It has now been sufficiently de- 
monstrated by Passarge in the Kalahari Desert of South Africa. For the past eighteen years the author 
has taught that the great desert- plains of Australia are one-time upland areas that have been truncated 
by the wasting action of subaerial erosion that has been continuous through many geological epochs. 

The Central Otago pefieplain lies in the arid belt of the South Island of New Zealand ; and its geo- 
graphical relationship to the western mountains of the main divide, and the prevailing trade .winds, has 
probably remained the same since early Tertiary times. It is thus conceivable that it is the result of 
arid erosion at a time when the surface of the North Island stood at a lower altitude than that of 

* Park : Read before the Mining Students' Association of Otago University, Julv, 1901. 
fPark: Bulletin No. 2 (New Seiies), N.Z. Geol. Surv., 1906, p. 6. 
I Park : Trans. N.Z. Inst., vol. xxxvii. 1904, p. 489. 



to-day, and that it has been elevated and dissected since the Miocene. 
make a decisive choice between these alternatives. 



At present it is impossible to 



Block Mountains. 

The district under re\-iew is occupied by high table-topped mountain-ranges intersected by deep 
watercourses, and separated from each other by river-valleys or cleft in twain by profound gorges. 

The mountain-ranges are the Dunstan Mountains and Pisa Range, with a mean elevation of 
5,000 ft., and the Carrick Range, some 500 ft. less. These flat-topped ranges are the remains of the 
old base-level plain of erosion of Central Otago, described in the wTiter's report* on the Alexandra 
area lying immediately to the south of this. 

A notable and nearly always a conspicuous feature of these ranges is the straight even outline of 
their slopes and the general absence of bold dominant spurs. The west slope of the Puketoi Range, 
the east side of Raggedy Ridge, and the east slope of Dunstan Range from Chatto Creek to St. Bathan's 
suggest the exaggerated glacis of some gigantic earthwork embankment furrowed by numerous small 
straight watercourses. 

Dunstan Range. 

This range lies between the Manuherikia and Cromwell basins. It extends from the Dunstan 
Gorge, through which the Clutha flows between Cromwell and Clyde, in a north-easterly direction for a 
distance of twenty-four miles, ending against St. Bathan's Range, which runs nearly due north and 
south, and from which it is separated by Dunstan Creek. 

The summit is fiat or gently undulating, and maintains a height of about 5,000 ft. above the sea 
from one end to the other. 

Along the eastern or Manuherikia side of the range there extends a great dislocation or fault- 
fracture, which is well exposed in the alluvial workings at Waikerikeri, Devonshire, Tinkers, Drybread, 
and Vinegar Hill. 

Along this zone of fracture the lacustrine beds which occupy the floor of the Manuherikia lake- 
basin are drawn down or faulted so as to stand on end. 

When we examine the structure of the Dunstan Range we find that the schists are disposed on 
each side, so as to present in profile the appearance of an inverted pudding-dish. On the table-topped 
summit the schists are hnng abnost horizontal. On descending the steep sides of the range, the inclina- 
tion of the rocks gradually increases until at the foothills the angle of dip is almost vertical. 

In the deep gorge of the Waikerikeri leading up to Leaning Rock, it is interesting and instructive 
to select some conspicuous band of schist and trace it in its upward course as it bends gradually from 
the vertical position at water-level to the nearly horizontal position near the summit of the range. 



cc 



" " o h « 



s/e: 



Fio. 1. Section across Waikerikeri Fault. 
a. Mica-schist. b. Lacustrine beds. 



The apparent stratigraphical conformity of the schists and Pliocene beds at Anderson's Creek, 
Waikerikeri, might possibly be due to tectonic folding, and not to faulting, but this is almost beyond 
the bounds of probability, judging from the e\adence furnished there and elsewhere. 

♦Bulletin No. 2 (New Series), N.Z. Geol. Sur., 1906, p. 6. 



10 

In the first place the schist is a hard unyielding rock, against which, in the progress of the sharp 
folding that would be necessitated by the existing circumstances, the clays and loose incoherent beds 
of sand, quartz grits, and gravels comprising the lacustrine beds would be crushed and distorted out of 
shape. But such is not the case. The succession of alternating clays and sands follow each other with 
perfect regularity and without any trace of crush or distortion, except along the line of contact where 
the soft shales are crushed as if by movement on the wall of schist. 

Moreover, at no other point along the zone of fracture is there the same conformity of strati- 
fication, although in some places it approaches it. 

Along the Ida Valley, Pisa and Baimockburu faults, there is always a wide divergence between the 
stratification of the schist and Pliocene beds, and in these places the tilted and involved position of the 
younger sediments can only be ascribed to faulting. 

The conformable bending of the schists and lacustrine beds at Waikerikeri is apparently an acci- 
dental happening such as might easily enough occur in the case of any two formations abutting against 
each other along a fault-line. 

The \aew held by the writer is that the flat-lying schists of the elevated peneplain were gradually 
drawn down and bent by subsidence along the great fault ; that the lacustrine beds were then deposited 
horizontally against the already inclined schists ; and that at the close of the Pliocene the newly 
deposited lacustrine sediments were involved bv further faulting along the same Hue of dislocation. 

The mechamcs of the fault-movement at Waikerikeri and elsewhere along the foot of the Dunstan 
Range presents no great difliculty. In the centre of the basin the lacustrine beds are generally hori- 
zontal, but along the foot of the Dunstan Range they are tilted at high angles, being in many places 
quite vertical, as shown below. 




Fig. 2. Section from Foot or Dunstan Range across Waikerikeri to Waituna Terraces. 

a. Sandstone gravels lying horizontal. 6. Sandstone gravels tilted. c. Quartz sands, grits, and clays. 

schist. 



d. Mica- 



The WTiter, as the result of his geological work during the summer of 1905-6, arrived at the conclu- 
sion that the Dunstan Range was a block mountain or horst, flanked on each side by narrow strips of 
subsidence. His ob.servations during the summer of 1906-7 are in no way inconsistent with that view, 
but rather tend to confirm it. 

The mamier in which loose or only slightly compacted fragmentary material may be tilted by 
faulting is well seen at the celebrated Blue Spur Claim near Lawrence. The actual appearance of the 
working-face, as seen by the writer early in November of 1906, is shown in the subjoined figure. 

The upturned position of the gold-bearing strata seems to have been brought about by an over- 
thrust or reversed fault. 




Fig. 3. Showing Section or Working-face of Blue Spur Claim, November, 1906. 
a, a^^. Pleistocene gravels, sands, &c. b. Mica-schist. 



3b ac^mpcavyBrdletinN^'S. Cronnwll SiLbdh.'istonWestem Otxigo Division 




JAMES MACKINTOSH BELL 

^^^ GcTivral Referenc e -.. ■■ ■ 
Roads ami Tracks ...t/in.-' - ^i z-^^:: 

Triij. Stations . .. M©)!/)' 

Watt^TBacee „_ ,.. . .. Br— if— 

Roaei Reserves -unformecC ., — ^-— =— = 



'i E ,' jL N I ^/—' Jf a \ \ 'R y o c 

GEOLOGICAL MAP OF 

Reference to Geological colours 

PLIOCENE PALEOZOIC 

RECENT PLEISTOCENE Manuherikia Sariee Maniototo Suriea 



TIGER HILL 



- Scale of Chains - 



^^ 



GeoUigy by James Park. 

Topographical data, mainly supplied by the 
lands and Survey Department, and in part orig- 
inal surveys by A.G.MI^Donald, A.M.Fmlayson., 
and PJ/.MSDoua.U. under direction of James Park 



s EH n □ 



Fs^ r^ 



lodn Lorn Bvo-Jn™... 2S5*-;Wftm,«.&m<4Bo:..G»>.fc Oay. « S«A Mica. Schtui OUWcrhys SiUs&rllcM,, 



LmwnbvKJCra^^ord.Jufi' '307 



11 

The fault-plane when freshly stripped is as smooth as a pavement. It strikes N.W.-S.E. and dips 
S.W. at angles varying from 22° to 27^°. 

The whole thickness of the Pleistocene gravels as well as the fault-plane are exposed to view from 
a to Cj in the present working-face, a^ being the floor of the claim. It is a unique occurrence to have 
the effects of faulting so clearly laid bare for the investigation of the geologist. (See frontispiece.) 



Pisa Range. 

This range lies on the west side of the Clutha, extending from the Kawarau Gorge northwards 
to the Luggate, a distance of some twenty-four miles. Its summit is a wide plateau, mostly fiat or 
gently undulating, ranging in height from 5,580 ft. at Mount Dottrell to 6,300 ft. at Mount Pisa. From 
these points the ground falls slowly away to the north and south as broad grass-covered slopes. 

Pisa Range forms the western rampart of the Cromwell basin ; and along the foot of the range 
on the west side of the basin there stretches a great dislocation, appearing at the surface as several 
parallel fault-fractures, which have caused involvement of the lower members of the lacustrine series. 

In the \'icinity of Pisa fault the schists are greatly disturbed, being in most places tilted on end 
or inchned towards the east or west at high angles ; but the general direction of dip after leaving the 
zone of disturbance is towards the north-west, at high but steadily decreasing angles, so that before 
the Roaring Meg on the western side of the range is reached the angle of dip is generally between 
30° and 35°. (See Section AA on sheet facing page 30.) 

Carrick Range. 

This range forms the southern barrier of the Cromwell basin. It is merely the northern continua- 
tion of the table-topped Gar^^e and Old Man Ranges. It ends at Mount Difficulty, which is separated 
from Pisa Range by the Kawarau Gorge. 

The summit is broad and almost flat, maintaining an elevation of about 5,000 ft. for many miles 
in length. 

Traversing the foot of the range behind Bannockburn in a nf)rth and south direction, there is a 
great fault, the course of which can be traced quite clearly by the tilting and displacement of the Pliocene 
lacustrine beds along its course. 

Along the fault-line the schists are standing nearly vertical, but passing westward the inchnation 
gradually decreases until at the sumnut of the range the rocks are fiat or gently undulating. 

The Carrick and Garv'ie Ranges are splendid remains of the ancient elevated base-level of Central 
Otago ; and, although doubtless nmch reduced in height by the long continued waste caused by 
atmospheric erosion, the original contour has been singularly well preserved. 

These ranges, although locally known under two names, in reality form one continuous flat-topped 
plateau, which is separated from the Remarkable Mountains by the shallow Nevis Valley. 



The Remarkable Mountains. 

The Remarkables are a chain of high broken mountain-peaks, rising over 2,000 ft. above the general 
level of the table-topped block ranges described above. They form the western boundary of the old 
base-level plain of Central Otago — a boundary as sharply defined as that of any modern valley, and 
requiring the exercise of little constructive imagination to see things as they once existed. 

The highest peak is Double Cone, which attains a height of some 7,600 ft. above the sea. Over 
against this, and about a mile and a half distant, is Mount Ramsay, 7,100 ft. Mount Geikie, 6,500 ft., 
and Mount Cruachan, 6,200 ft., form the northern termination of the Remarkables, the former throwing 
off a great ridge that ends abruptly at the Ne\-is Bluff. (See Map facing page 21 . ) 

The crest of the range throughout the greater part of its length is an excessively narrow saw-backed 
ridge, a feature that presents a marked contrast to the broad table-topped block moimtains of Central 
Otago. 



12 

The Remarkables, with a crest-line from 7,000 ft. to 7,600 ft. high, rise steeply from the shores 
of Lake Wakatipu by a series of stupendous declivities, forming a spectacle that for absorbing 
grandeur is unrivalled in Xew Zealand, a country justly famed for the beauty of its alpine scenery. 

The primitive Maori in myth and legendary story peopled the imknovm land beyond this weird 
sky-cleaving rampart with malicious turihou, ill-doing fairy, and dread monster. 

On the east side of the range the descending spurs gradually merge into the great Dunstan pene- 
plain, which stands at an elevation of 5,500 ft. to 5,000 ft. 

Notwithstanding their great height, the Remarkables carry no permanent snowfields of any moment, 
but the marks of ice erosion are to be seen everywhere up to the 6,000 ft. contour. The vide saucer- 
shaped basins lying at the sources of Doolan's Greek, Conebum, and Bnmidary Creek, dotted with 
tarns and traversed by deep U-shaped gutters, afEord the clearest evidence of prolonged glaciation. 

Rock Pillars and Knobs. 

The even summit of the Dxmstan Range is broken here and there by groups of pillar-Uke stacks 
and castellated piles, or tors, of mica-schist. The pillars often possess sharp outhnes and nearly 
vertical sides. They sometimes attain a height of 70 ft. or 80 ft., and are foimd on all the schistose 
block mountains of Central Otago. 

They are merely masses of horizontal or nearly horizontal schist that are intercepted between 
two or three joint-planes, and have been left standing while the surrounding rock has been worn away 
by subaerial denudation. 

These rock-piles do not appear to be harder than the adjacent schist, and their greater immunity 
from degradation must be due to some accident of situation or direction of jointage. They are found 
wherever the schists lie more or less horizontally. 

Tabular masses of similar origin are dotted about the grass-covered Barewood and Taieri plateaux, 
but they never attain the height of those on the exposed summits of the Rock and Pillar, Old Man, 
and Dimstan Ranges. 

One of the most conspicuous of these obelisk-hke monoliths is situated on the Old Man Range at 
the south end of the Manuherikia Valley. (See Plate I ) 

The beautifully even outline of the summit of the Hawkdun Range, which is composed of mud- 
stones and greywacke, and forms perhaps the best-preserved example of the great group of block moun- 
tains in Central Otago, is unbroken throughout its great length by any protruding knobs or crags. 

Genesis of Pisa and Carrick Horsts. 

Briefly recapitulating the facts recorded in the preceding pages, we find that these ranges are 
composed of Palaeozoic mica-schist, containing subordinate bands of chlorite-schist ; and that the 
lower flank of each range is traversed by a great dislocation or fault-fracture, along which the Pliocene 
lacustrine beds are deeply involved among the schists. The schists are also steeply tilted, and, where 
the dislocation comes to the surface as two or more branching faults, they are often broken into a 
jumble of shattered rock or bent into a tangle of complex folds within the zone of fracture, which varies 
from a few chains to 20 chains wide. 

Embayed by the Dunstan Mountains on the east, by the Pisa Range on the west, and the Carrick 
Range on the south, lies the Cromwell Flat, the site of an old lake-basin, in which a pile of sediments 
was deposited in Pliocene times. 

At the close of the Pliocene and before the advance of the glaciers, the lacustrine deposits were 
tucked in among the schists along the western margin of the old basin by a downward movement on 
the hangihg-wall of the Pisa fault. 

The mechanics of this movement is somewhat difficult to follow. It may have been a slow pro- 
gressive thrust, first bending and then breaking the rocks, or a sharp shp or succession of slips along 
an existing line of fracture. In whatever way the stress operated, it appears that a condition of static 
equihbrium was established after the tilting of the Pliocene strata. No trace was found in the Crom- 



PLATE I. 




OuELisK u.\ Oi.u Man KaMjI:;: A Tyi-ical ItocK-i'ii.i.Ai; 



Bulletin No. 5.j 



[To fads p. 12. 



PLATE II. 




DuLHI.K Cu.SE, NuUTil K.NU Ol KlCMAliKAHLliS, HiO.M Hk.M) OK Dooi.ANS C'ltlCKK. 




Double Coxk, North End of Kemahkable^, showing Lake Alta Cihque, taken fkom Mount 

PiAMriAY, 7,100 ft. 

Bulletin No. 5.] [^o face j}. 12. 



PLATE HI 




LaKK AlTA, 1>,U5U IT., AT FuUT OK DuLlil.E Cone, liEilzUJKAULKS. 



biiilelin No. 5.] 



[To face p. li. 



13 

well basin of any movement that had affected the glacial and fluviatile debris of the Pleistocene. That 
such movement will yet take place seems quite within the bounds of probability, if we ma}' be permitted 
to draw an inference from the occurrence of spasmodic slippings that have taken place in recent years 
along the course of the great Kaikoura fault — slippings that propagated destructive seismic waves. 

In the Manuherikia basin it is different. On the west side of the valley, close to the great Wai- 
kerikeri fault, in the old allu\-ial workings in Anderson's Gully, the glacial drifts are found to be displaced 
by many small faults that can only be explained by referring them to comparatively late movements 
along the major fault. 

Thus we have several more or less parallel block mountains that were once portions of an 
elevated base-level plain, each range with a great line of fault-fracture running parallel with its main 
axis, and intervening valleys that were once lake-basins. 

That the origin of the mountains is referable to the great faults seems irresistible. The problem 
to be solved seems to narrow itself down to this : Do these plateau-like mountains owe their height 
to uplift or to the subsidence of the adjacent valleys ? 

It seems to present fewer difficulties to believe that the lake-basins are grahen or strips of subsidence, 
and the flat-topped ranges horsts or walls that have been left standing at the original level of the elevated 
peneplain. 

The Systematic Investigation of Block Mountains. 

The distinguished Professor W. M. Davis, of Harvard University, is profoundly interested in what 
he terms the '" remarkable group of block mountains in Central Otago,"' first described b)' the author 
in Bulletin No. 2, New Zealand Geological Survey (New Series), 1906, and in a recent letter discusses 
the elements that seem to him ideally desirable in the systematic investigation of block mountains. 
His scheme seems to fulfil all the requirements of a comprehensive physiographic and geological study, 
and should prove helpful to the field geologist and student, in that it is suggestive of points that are 
liable to be overlooked. It is as follows : — 

(a.) A general statement of the geological structure of the region, with details added later 

when needed. 
(6.) The stage of erosion reached when block-faulting took place. 

(c.) The relation of the fault-lines to the pre-existent structural lines and topographical features. 
(d.) The number and attitude of the heaved and of the thrown blocks. 

[e.) Systematic account of the main drainage - lines, sufficient to show whether they persist 
from the previous cycle as antecedent streams in spite of adverse faulting, or 
whether they are revived into renewed activity by favouring deformation, or whether 
they are of new generation, consequent upon the slope of the tilted or faulted faces 
of the displaced block; , or whether they are developed as subsecjuent streams by head- 
ward erosion along ne.vly exposed weak structures. 
(/.) Definite indication of the stage reached on the heaved blocks (separate statement being 
made for resistant and for weak rocks) ui the work of erosion by the several kinds of 
streams, and in the work of gradation by general weathering on the fault-faces and 
valley-sides, with particular reference to the manner in which the features produced 
in the new cycle are related to those which hold over from the previous cycle and to 
those produced directly by faulting. 
{(J.) Indication of the stage reached in the work of aggradation (and afterwards of degradation) 

over the thrown blocks. 
(h.) As many specific instances as possible, not described empirically, but always in reference 
to the above-named elements. 

Cromwell Basin. 

This basin is bounded by the Dunstan Range on the east, by the Pisa Range on the west, and by 
the Carrick Range on the south. It extends along the Clutha as far as the Lindis flats. There is no 
evidence to show that it ever extended up the present valley far beyond the junctioi; of the Tarras. 



14 

The floor of the valley is occupied by a great thickness of lacustrine sediments. On the east 
side of the basin these beds dip towards the centre of the basin at angles varying from 20° to 30°. 
Towards the dip the inclination gradually decreases, and before the centre of the basin is reached the 
beds are lying flat. 

Along the foot of Pisa Range the lacustrine beds are incUned at high angles, ha\'ing been uptilted 
by the subsidence of the ground on the east side of the fault. 



Pisa Range 



Five Mile CI' 



DvrsUn Rang? 
Chthj Rivor ; 

s.e. 




Fig. 4. Section feom Pisa Range across Five-mile Creek to Clutha River. 
a. Sandstone gravels (Maori bottom). h. Clays, sands, shales, and lignite. c. Mica-schist. 



Sharp tilting of the lignitic series has also taken place along the fault-zone running parallel with 
the flank of the Carrick Range. 

There is no visible sign of faulting on the east side of the basin, and if any faulting has taken place 
it must have occurred prior to the deposition of the lacustrine series, which rests on the schists without 
any appearance of disturbance. 

There is much faulting at Bannockburn coalfield, lying in the south-east corner of the basin ; but 
the writer believes that it belongs to the system of dislocation of Pisa and Carrick Ranges, and not 
to a separate system on the east side of the basin. (See sections of Bannockburn : Special map.) 

The Pliocene lacustrine beds are overlain unconformably by fluviatile and glacial drifts formed 
during the Pleistocene period. 

The basin is drained by the Clutha and Kawarau Rivers (see Plate XIII). The united rivers, 
known as the Clutha, leave the basin near Cromwell, flowing over a rock ledge on which there rests 
from 10 ft. to 20 ft. of travelling gravel, according to the height of the river and prevalence of floods. 
The height of this rock ledge is about 640 ft. above the sea. 

The depth of the old shaft at the coal-mine at Chinatown, a few hundred yards above the junction 
of the Kawarau, is 145 ft. The height of the normal water-level of the Kawarau at the coal-mine is 
710 ft. and of collar of shaft 725 ft. Taking the depth of the shaft from 725 ft., we get 580 ft. as the 
height of the bottom of the shaft above sea-level, or 60 ft. deeper than the present outlet. 

Two boreholes put down at water-level on the Clutha river-flat, about half a mile above Dead- 
man's Point, reached a depth of 50 ft. without reaching the schist floor. The river-level here is 715 ft. 
above the sea. Taking 50 ft. from 715 ft. we get 665 ft. as the height of the point reached by the bore- 
hole, which was still in the coal-measures. 

Comparing the bottom of the shaft with the height of the rock ledge over which the Clutha flows, 
we discover that the basin near the rim is deeper than the outlet. How much deeper the centre of the 
basin may be there is no evidence to tell, but it may well be some hundreds of feet. 

At the upper end of the Dunstan Gorge, facing Cromwell and only some 15 chains distant from the 
east end of Cromwell Bridge, there is a heavy deposit of river-gravel forming a terrace, the summit of 
which is 400 ft. above the rock ledge in the bed of the Clutha near by. 

The reservoir for the domestic water-supply of Cromwell has been excavated in this terrace. 

The gravels extend back into Brewery Creek, and altogether cover an area of several acres. They 
are composed of well-rounded detritus, among which sandstones, grejwacke, and quartz are well repre- 
sented. Masses of mica-schist, generally in flat pieces with rounded edges, are common, and do not 
appear to have travelled far. 



15 

Scattered throughout these gravels, and more conspicuous for their size and colour than their 
abundance, are rounded boulders of basalt, both the smooth and pitted varieties described by the writer* 
in his report on the Alexandra district, being present. 

In addition to these rocks there are also present, but few in number, small pebbles and boulders of 
pink quartz-schist, a rock which occurs as large angular masses on the back of Clyde moraine,f along the 
track leading across the moraine from Clyde to Dairy Creek coal-mine. 

The sandstones and grepvackes, u-ith which also occur occasional boulders of gritstone, breccia, 
and conglomerate belonging to the same formation, are foreign to the Cromwell basin and are not found 
in situ nearer than the head of Lake Hawea. The basalts and pink quartz-schist are known to occur 
in situ in Black Peak and Mount Alta on the west side of the Matukituki River, which flows into the 
lower end of Lake Wanaka. They are not known to occur nearer than this. The gravels of this high- 
level terrace are t^'jjical Clutha gravels, and their presence clearly marks the site of the high-level outlet 
of the Clutha River. 

Near'the lower end of the high terrace, and about half a mile from Cromwell Bridge, there is an old 
river-chaimel running through to Brewery Creek, between Bastion Rock and the spur on which the 
high terrace-gravels rest. Below tliis there is the river-terrace, along which the coach-road inns to 
Clyde. 

The high terrace, the Bastion chaiuiel, and the road-terrace all mark successive levels at which 
the Clutha ran before it had cut down its channel to the present level. 

ORIGIN OF CROMWELL BASIN. 

Here we have a mountain-girt valley — a true rock basin possessing an overflow cut in the solid 
rock. In considering its origin we seem to have only two contentions open to us. Clearly, we must 
conclude either that the basin is an ordinary' valley of erosion that became blocked by the difEerential 
tilting of the lower end, or that it is a tectonic valley. If the latter, it is either an area of subsi- 
dence or an area left behind, the table-topped ranges forming the walls of the basin being the uplifted 
portions of an ancient plain of erosion. 

The floor of the valley, as we have seen, is occupied by a series of fresh-water sediments that are 
much disturbed along the south and west sides of the valley. On the upturjied edges of this lacustrine 
series there rests a great pUe of morainic drift that can clearly be traced to the Pleistocene advance 
of the glaciers, after the retreat of the ice-sheet that covered Otago and Southland. 

The sediments forming the lacustrine beds are such as one would exjject to be depo.sited in still 
shallow water. They contain no trace of glacier-debris or ice-action such as would manifestly be 
present in a basin of such depth and extent if excavated by ice or by ice and fluviatile action working 
together. 

There is no evidence known to the WTiter of glaciation in New Zealand in the Miocene period. 
On the contrary, the fauna of the Miocene sea is that of a fairly warm or temperate climate. Nor is 
it probable, from what we now know of the Middle Tertiary, that the structural features ,of the land 
were such as to favour the accumulation of great masses of ice on the high lands of that time. 

The geographical distribution of the Miocene strata shows that oidy the mere skeleton of our 
axial mountain-chains stood above sea-level in the Miocene, and that, too, at an elevation probably 
3,000 ft. or 4,000 ft. lower than at present. 

Manifestly the origin of the basin cannot be ascribed to ice erosion. 

Putting, the i, ice erosion aside, we are left Avith fluviatile erosion actijig by itself. The problem 
before us is : Can we find sufficient evidence to warrant the view that the Cromwell basin is merely 
a blocked-up portion of a river- valley excavated in a Miocene plateau, or, what would be more probable, 
a valley excavated in a region of slow uplift, the excavation being progressive with the uplift ? 

The chief feature in favour of this view is the existence of the present valley. 

The present outlet is not at the lower or south end of the basin, but at Cromwell, which is situated 
three miles from the end. If the basin is a portion of an ancient valley of erosion it is reasonable to 

♦ Bulletin No, 2 (New Series), N.Z. Geol. Sur., 1906, pp. 46, 47. f ^"c. cit., p. 19. 



16 

suppose that the former extension of the valley would be southward — that is, in a direction continuous 
with the present trend of the valley. 

The Carrick Range lies athwart the Cromwell basin, and it is to its uplift that we should have to 
ascribe the blockiug-up of the valley. But we have already shown that the table-topped Carrick 
Range and the group of table-topped ranges with which it is connected are a portion of the elevated 
plateau of erosion of Central Otago. Further, the Pisa and Dunstan Ranges, which form the side walls 
of the basin, are also portions of this old base-level plain. 

Here we are faced with the mechanical difficulty of constructing an uplift that would cease to 
rise when a height uniform with that of the previously existing table-topped Pisa and Dunstan Ranges 
had been reached. Prolonged regional uplift would certainly be accompanied by warping, of which 
there is no exidence. 

If we assume that this old lake-basin is a tilted valley we should naturally expect to find the 
floor covered with the gravels and alluvial detritus always found along the course of a river. The tilting 
or uplift that impounded the water would also trap the detritus carried down by the river flowing into 
the upper part of the basin. 

Such fluviatile material, if present, should be found underlying the lacustrine sediments. In all 
the sections where the lowest beds are exposed — as, for example, at Bannockburn, Shepherd's Creek, 
Adam's Gully, Pipeclay Gully, Kawarau Gorge, Lowburn and Five-mile Creeks, and Quartz Reef 
Point — there is an entire absence of fluviatile drift of any kind at or near the base of the fresh-water 
deposits. These latter consist of hundreds of feet of clays mixed with quartz sand and grit, or of 
drifts of quartz sand and grit, in which the quartzose material is commonly rough, angular, and of a 
fairly uniform size, mostly imder half an inch in diameter. 

The same absence of fluviatile drifts at the base of the lacustrine series is found in the Manuherilda 
basin, where the uptilted beds are well exposed at Alexandra, Clyde, Blackman's, and Waikerikeri in 
the lower end, and at St. Bathan's, Marion Creek, and Hill's Creek at the north end. 

The Manuherikia basin is a long narrow quadrilateral running north-east-south west, and bounded 
by appro.ximately parallel faults on the opposite sides. The Manuherikia River enters the basin at 
the north corner, coming in through a narrow gorge. 

The lacustrine beds occupy the floor of this basin from the foot of the Old Man Range at the lower 
end to the foot of the Hawkdun Range at the north end. Thus we find that the present valley is 
practically coextensive with the old lake-basin. If, then, the basin is a valley of erosion blocked by the 
Old Man Range at the south end, we must also assume that its upper end was blocked by the uplift 
of the Hawkdun Range, except we are willing to concede that the Manuherikia was able to excavate 
a valley as wide at the upper end as at the lower, and with approximately straight sides and head. 

Assuming, however, that the Manuherikia River did excavate the valley of that name, and that 
the tilting of the land blocked the end of the valley so as to form a lake-basin, it is obvious that the 
Manuherikia would still continue to drain into the basin, discharging a load of debris at the upper end. 

The area drained by the Manuherikia is composed of sandstones, greywacke, and mudstones. 
Hence we should expect to find gravels composed of these rocks at the base of the lacustrine series. 
But we know that they are entirely absent ; and, as shoWTi by the writer"' in 1906, it was only after 
600 ft. of comparatively fine clayey and quartzose lacustrine sediments had been deposited that we 
obtain the first trace of sandstone gravels in the basin. 

The evidence seems almost conclusive that the Manuherikia basin existed long before the river 
of that name found its way into the basin ; long enough, at any rate, to allow the accumulation of 
many hundreds of feet of fine sediments, and the growth of sufficient vegetation to form thick seams 
of lignite. 

The Cromwell, Manuherikia, and Ida Valley basins are parallel and bounded by fault-fractures 
giving approximately straight sides. The geological and physiographical features are the same in 
each, and clearly point to a common origin. 

Whatever the origin may be, we find that the evidence obtainable in the Cromwell and Manuherikia 
basins does not warrant us in concluding that these ancient lake-basins are tilted valleys of erosion. 



* Bulletin No. 2 (New Series), N.Z. Geol. Sur., 1900, p. 10. 



17 

Moreover, if they are valleys of erosion, it is obvious that the excavation and tilting must have 
taken place in the Upper Miocene — that is, prior to the deposition of the Pliocene lacustrine series. 

But the lacustrine sediments wrap around the flanks of the surrounding ranges, abutting close 
xinder the straight ascending slopes, which have suffered less deformation than one would naturally 
associate with features formed in the Miocene. 

The facts presented in the Cromwell basin are not inconsistent ■Rnth the facts relied on bj' the writer 
in 1906,* when he expressed the opinion that the lake-basins are areas of subsidence, and that the pile 
of lacustrine sediments found in each was deposited in a shallow but steadilv sinking basin, in which 
the rate of deposition for a long period about kept pace with the rate of subsidence. 

HISTORY OF CROMWKLL BASIN. 

The history of the basin must be constructed from the existing geological data. 

The existence of an ancient lake in this area is jjrovcd by the great scM'ies of fresh-water sediments 
seen everA-where hnng on the floor of the valley. 

A very complete section of these lake-beds is exposed in the floor of the old alUnnal workings lying 
between the Bannockburn Post-office and the foot of Carrick Range. The beds are there disposed in 
a shallow synclinal fold, exposing the basement nu-inbers of the series on both sides of the fold. 

A fine but less complete section of the same beds is exposed on the bank of the Kawarau, in the 
allux-ial workings half a mile from Cromwell. (See section facing page 32.) 

Tlie section at Bamiockbiiru exposes some 1,000 ft. of strata in an unbroken sequence, consisting 
mostly of clays, quartzose sands, and grits, with seams of lignite and beds of shale containing leaf- 
impressions and casts of fresh-water shells. 

The great thickness of fine material forming the lower beds indicates the prevalence of quiet con- 
ditions of deposition for a considerable time, and provides evidence that no large rivers or torrential 
streams drained into the lake at this period. 

The material itself is clayey or quartzose matter of such a nature as would be derived from the 
slow weathering and denudation of the neighbouring mica-schist, occujjpng a land-surface of moderate 
relief. 

The seams of lignite near the base of the series show that after the schist floor of the basin had been 
levelled by the quartzose grits and muds a mixed vegetation, probably dense and luxuriant, established 
itself on the shores of the lake, which could only have been a long narrow strip fringed with swamps and 
shallow lagoons. 

After a period of growth, the durati(m of which can only be surmised, the accumulation of peat 
bog and forest-matter was buried beneath a deposit of clays and sands. 

During the growth of the vegetation there was either a cessation of the subsideiuM', or an extremely 
slow rate of movement, not sufficiently rapid to .submerge the forests and swam])s on the margin of the 
lake. 

The covering of the vegetation by clays and sands points to a renewal of the subsidence or to an 
accelerated downward motion. 

At several points in the overlying succession of sediments there are small seams of lignite, each of 
which indicates a complete or partial cessation of the downward movement aocompanied in each case 
by an invasion of the basin by a fresh growth of vegetation. 

How long the land paused or remained at rest when the peat bogs grew is a matter of some uncer- 
tainty. The growth of a peat bog is naturally dependent on the nature of the flora, and is always slow. 
In some cases bogs increase in thickness five or six inches every year, and in some cases there is no 
increase. t The average growth is probably not more than three inches a year. 

If we assume that 10 ft. of peat will make 2-5 ft. of lignite and that the growth of the peat bog 
amounted to, say, Sin. every year, then every foot of lignite will represent a pause or cessation of sub- 
sidence of sixteen vears. 



•Bulletin No. 2 (New Series), N.Z. Geol. Sur.,1906, p. 9. t Johnson: "The Irish Peat Question"; The 

Econoihic Proceedings of the Royal Dublin Society, vol. i, p. 1. Also G. H. Ashley : " Maximum Rate of Deposition 
of Coal " ; " Economic Geology," vol. ii, p. 34. 

i — Cromwell. 



18 

Calculated on this basis the 7 ft. seam in the Excelsior Mine at Bannockburn would represent a 
period of growth of 112 years. There are several seams of lignite near the base of the series, and they 
indicate pauses of longer or shorter duration according to their thickness. 

After a time, subsidence seems to have been continuous. The sediments gradually became coarser 
until the cycle of lacustrine deposition was ended. Hitherto the materials had been derived from the 
surrounding schistose mountains ; but another agency bearing a new kind of material now appeared 
on the scene. 

The lacustrine beds, as so well seen at Lowburn, are covered with a great thickness of gravels mainly 
composed of sandstones and greywackes, all of which are foreign to the district. The presence of these 
gravels bears silent but graphic witness to the great transporting and constructive power of the new 
geological force which had thus suddenly come into being. 

Here we have our first acquaintance of the Clutha River, bringing with it the beginning of the 
system of drainage that has continued right up to the present time. 

These ancient gravels, yellowish-brown and rotten, are known throughout the goldfields as " Maori 
bottom." 

It is a significant fact that the sandstone gravels do not contain the basalts and pink quartzite 
brought down the Clutha Valley at a later date. 

The Clutha poured its rocky drift into the basin until the lake was filled up, the new flood-level 
being a shingle plain extending from one side of the valley to the other at a height some 600 ft. above 
the present river-level. 

The outlet of the basin was now and had been for some time at Cromwell, and it was doubt- 
less the cutting-down of the rim that enabled the Clutha to carry its load do•v\^^ to the south end of 
the basin. 

How long the Clutha remained in sole possession of the basin is impossible to determine, but it was 
probably not long after the filling-in was complete that the Kawarau foimd its way into the south end ; 
and with its advent there began a new cycle of events. 

The united rivers now wore down the outlet at a rapid rate, and soon began to cut out and carry 
away the newly formed lacustrine sediments. Along the lower end of the vallej' the lignitic measures 
were denuded down to the bed-rock, and over all the basin the upper members were completely shorn 
away, excepting a strip of " Maori bottom " along the foot of Pisa Range and a patch at Quartz Reef 
Point, the cycle of denudation proceeding in the inverse order to the above statement. That is, when 
the erosion and removal of the Phocene beds began, the Clutha and Kawarau ran at a height some 
600 ft. above their present level, hence the first beds removed were those last formed in the preceding 
cycle of construction and reclamation. 

It was about this time that the lacustrine beds became involved in the fault-fractures along the 
flanks of the Pisa and Carrick Ranges. 

Whether this tucking-in of the Pliocene beds was due to the uplift of the ranges, or the subsidence 
of 'the valley, or whether the changes that must have accompanied such faulting had any connection 
with the subsequent events, is not quite clear. We do know, however, that the rivers that had been 
destructive now became constructive. 

The Clutha and Kawarau Rivers, after scouring out the lacustrine beds into wide terraces and 
benches, at once began filling up the excavation with sands and gravels. This was a period of great 
fluviatile activity, and it continued until the basin was once more a shingle plain stretching from one 
side of the valley to the other, at the elevation of the Reservoir terrace opposite Cromwell. 

It is obvious that such building and filling-up could only have been made possible by the blocking 
up or raising of the outlet, either by ice and glacial debris, or by the uplift of the lower[|end of the 
valley, or by the subsidence of the basin. 

The presence of the moraine at the mouth of the Kawarau tells us that the action of the Kawarau 
was aided by a powerful ally in the shape of a glacier that descended the Kawarau Gorge, and stacked 
its rocky load among the drifts being carried down by the river. 

The Kawarau Gorge was the stronghold of the glacier, and to this narrow defile it climg tenaciously, 
its terminal face seldom advancing more than half a mile from the end of the gorge. 



7b ajxompcauy Szdletirh N°S, Cro-nwvell SxihdxvtstoTiWesterrv Otago Divistorv. 




' by James Park. 
Topographical data, mainly supplied hy the 
Lands and Survey DepartTnent, and in part ori^ 
inal surveys hy A. CM^-Donaid, A M.Fmlaysan,, 
and P.H.MSDou.all. under direction of James Park. 



Drawn "by R. J. Crawford, Septemher 1907. 



By Authority - John Mackay, flow 



20 

At these places there are long strips of lacustrine sediments consisting of quartzose sands, clays, 
shales, and brown coal. The strips vary from a few chains to a quarter of a mile vdde, and they are 
in every case tilted against the schist, and always much crushed. 

ORIGIN OF DEFORMED LAKE-BASINS. 

The evidence is too meagre to enable a satisfactory conclusion to be arrived at with respect to 
the genesis of these old basins. It is noteworthy, however, that the sediments are such as would be 
derived from the disintegration of the neighbouring mica-schist, and that they occur along a fault- 
fracture in each case. 

The basins contain no sandstone, greywacke, or other foreign material. Their deformation bv the 
Kawarau and its tributaries afiords conclusive e^^dence that they were filled with sediments some 
time before the excavation of the Kawarau Valley and the advant'e of the glaciers in the early Pleisto- 
cene. This we see is not inconsistent with the life-history of the Cromwell lake-basin. 

The different levels at which the patches of lignitic measures occur would tend to show that trans- 
verse faulting also aided the existing streams in deforming the original basin. 

It may well be. although we have no evidence of it, that the strips of lacustrine sediments are merely 
the remains of a greater formation that have been protected from destruction by their entanglement 
along great fault-dislocations, or by in-folding in great isoclinal folds. It should be noted that the 
Roaring Meg and G-ibbston strips of lacustrine coal-measures are about parallel to each other, and 
that both coincide with the axes of folding of the enclosing schists. Both strips occur in the area where 
the schists appear to have increased enormously in thickness. 

Valleys of Erosion. 

Of these the most important are the Dunstan and Kawarau Gorges. Of secondary importance 
are the Arrow. Soho, Motutapu, and Cardrona Valleys. 

Dunstan Gorge. — This is the channel connecting the Cromwell and Manuherikia basins. It is 
narrow in the bottom and bounded by steep rocky sides for a height of 600 ft or 800 ft., above which 
the vallev widens out, in most places ascending by easy slopes which here and there show signs of 
benching by ice erosion. 



Dunstan Range 




P^G. 6. Section across Dunstaij Gorge. 

Captain Hutton* considered that the entrance to the gorge at Cromwell was too abrupt and narrow 
to have been the outlet of a large body of ice, and for this reason surmised that the Clutha glacier found 
its way into the Manuherikia basin by the Bannockburn, Forkburn Creek, and Fraser River. 

The writerf showed last year that the gravels of the Fraser opposite the Bannockburn Saddle 
were composed solely of schist debris, the typical gravels of the Clutha being entirely absent. 

The recent examination of the Bannockburn Valley shows that the Clutha and Kawarau gravels 
do not encroach further than the mouth of Shepherd's Creek on the north side and Pipeclay Gully on 
the south. The gravel terraces exposed in high steep faces at Bannockburn are entirely composed 
of schistose material. The rocky debris carried by the united Kawarau-Clutha glacier is confined 
to the Cromwell basin and Dunstan Gorge. 



* " Geology of Otago," p. 91. f Bidletin No. 2 (New Series), N.Z. Geol. Sur.. 1906, p. 10. 




^ 



21 

But the uarro'mies's spoken of by Captain Huttou is tnie only of the bottom of the vallev, or gorge 
proper, the excavation of which took place since the retreat of the glaciers. Besides, it should be noted 
that the moraine at Clyde and the traces of ice erosion to be seen at the entrance of the gorge and on 
the shoulders of the spurs both escaped the notice of that author. 

The Dunstan Gorge owes its origin to fiuvio-glacial erosion, in places at least, acting along the 
plane of a rock-dislocation. 

The Kawarau glacier did not appear in the Cromwell basin until the PUocone lacustrine beds had 
been tilted and denuded, or not until the Pleistocene. 

The Kawarau Gorge. — This is the channel connecting the Arrow Flat and the Cromwell basin. 
In the bottom it is a narrow gorge, bomided by steep decli\'ities. Only at two places — namely, at 
Gibbston and Victoria Flat — docs it widen out so as to afEord a strip of level land suitable for settle- 
ment. Its course is very tortuous, and has been to a large extent determined by rock-dislocations 
following the line of fault-fractures. 

The excavation of the valley is the result of fiuvio-glacial action ; but the deep narrow channel 
in which the river now rims has been eroded by the river itself in comparatively recent times. 

The existence of a large moraine at the Cromwell end of the gorge has alreadv been recorded. 
Another and larger moraine occupies the floor of the valley between Victoria Bridge and Nevis 
Bluff. , 

At Gibbston Flat there is a good deal of mora:nic matter ; and several roches moutonnees running 
parallel with the valley remain as an evidence of prolonged ice erosion. 

Standing in the middle of the valley a short distance above the Kawarau Bridge there is a con- 
spicuous ice-sculptured hill ; and hnng on the east side of the Arrow River there is the Crown Terrace, 
so well known throughout Central Otago for its fertile soil and abundant crops. This liigh terrace 
is a broad shelf excavated in the sohd rock. The back of the terrace is covered with rich soil and 
gravel spread over it by the small streams that descend from the Crowu Range. 

Facing Arrowtown, the terrace is surmounted by flu\io-tilacial drift.s in which sandstone and 
greywacke are largely represented. Patches of the same high-level driits can be seen perched along 
the valley of the Arrow as far as the Soho jimction. 

There are no sandstones or gre\wacke within the present watershed of the .Arrow, a fact which 
invests the source of these gravels with an exceptional interest. 

The evidence of glacial erosion is strongly impre.sscd on all the land-features in the region lying 
between the Arrow and Lake Wakatipu. Soft flowing outline and rounded contour are seen on all the 
hills ; while the floor of the Arrow Flat rises and falls in long gentle ice-shorn hummocks that trend 
towards the Kawarau. 

This part of the district belongs to a distinct physiographic province, the detailed examination 
of which must be carried out before a correct generalisation can be made of the changes that have resulted 
in the development of the present land-forms <uid drainage-systems. 

Lakes and Mountain-tarns. 

The only sheet of water deserving the name of " lake " is locally known as Lake Alta, which lies 
immediately mider the Double Cone, Remarkable Mountaiits, at a height somewhat over 6,000 ft. 
above the sea. It is 33 acres in extent, as determined by the writer by actual survey. There is no 
means available at that elevation for soimding the lake, but so far as can be seen from the sides it 
appears to be shallow. (See Plate III.) 

This lake apparently owes its origin to the blocking-up of its lower end by the tumbled rocky debris 
piled there by the small glacier which at one time occupied the present site of the lake. 

A small rock-tarn lies on the high flanks of the Single Cone, about half a mile from Lake Alta ; 
and a shallow pond lying imder Mount Ramsay is the source of the second branch of Boundary Creek, 
which drains fhe beautiful cirque in which lies Lake Alta. (See Plate II.) 

Two rock-tarns, somewhat smaller than Lake Alta, he on the ice-cut shelf on the south-west side 
of Doolan's Creek, near the source of that stream and not far from Double Cone. 



22 

Rivers. 

The Cromwell district is traversed by two great rivers — namely, the Clutha, wliicli drains the 
Wanaka and Hawea watersheds, and tie Kawaiau, which drains Lake Wakatipu and the intervening 
country. Both rivers derive their main supply from the extensive snowfie!ds and glaciers perched 
on the summits and flanks of the r.iountxins of the main tectonic axis and the giant subsidiary ranges 
that descend therefrom. Their Q ow is thus practically independent of the rainfall in the lowlands. 

The bed of the Clutha from Deadman's Point to Clyde, and thai of the Kawarau from Cromwell 
to Lake Wakatipu, are deep, narrow, and steep, with the result that the waters hurry seawards with a 
velocity not often seen in rivers of their magnitude. 

The greatness of these rivers is not apparent. To the observer they are disappointing, their actual 
volume being dwarfed between steep rocky walls. 

At normal summer level the Kawarau was estimated by the writer to carry 10,500 cubic feet of 
water per second, and the Clutha 14,500 cubic feet. These estimates agree closely with those made by 
Mr. I. Orchison, Government Inspector of Telegraphs for Otago. 

Flowing at the mean rate of 2 ft. per second, the united rivers would present a flood 1,000 ft. wide 
and 12'5 ft. deep — a truly magnificent spectacle compared with the insignificant streak of water rushing 
through the Dunstan Gorge. 

The potential energy represented by the united streams, and running to waste day and night for all 
the year, and every year, is almost incredible. The total flow of water falhng only 10 ft. would develop 
25,000 actual horse-power, and falUng 100 ft. 250,000-horse power. Here we have a national asset that 
will be of incalculable value in the hands of posterity. How to utilise this great flood is a problem that 
can only be solved by engineering skill and the expenditure of large sums of money. 

The Clutha receives no large tributary in the Cromwell area, but from the flanks of Pisa and Dun- 
stan Ranges there descend a number of small streams that were for many years of great value for alluvial 
mining. They are now used for the irrigation of a number of prosperous farms. 

The chief tributaries of the Kawarau, within our present limits, are the Nevis and Roaring Meg. 

The Nevis, in the early part of March, after a summer of exceptional dryness, was carrying about 
80 cubic feet of water per second — that is, eighty Government sluice-heads* — and of this amount 
Doolan's Creek was contributing about 8 cubic feet. By constructing a dam at the narrow gorge 
immediately below the junction of Doolan's Creek, the Nevis could be harnessed so as to yield a 
useful amount of electric energy at a comparatively low cost. 

The Roaring Meg drains the west side of Pisa Range. For the last few miles of its course it is a 
picturesque mountain-torrent beating itself into a mass of white-crested foam in its headlong rush 
around and over the boulders piled in its steep bed. Next to the Nevis it is the most important branch 
of the Kawarau in the area under examination, its importance l}'ing in its never-failing flow, the great 
altitude of its valley, and its comparative nearness to Cromwell. (See Plate IV.) 

In February its discharge varied from 12 to 15 cubic feet of water per second, but this did not repre- 
sent its total flow, as the Crifiel Lead Sluicing Company was at the time diverting as much as the above 
into the Cardrona watershed. 

The valley of the Roaring Meg above an altitude of 2,000 ft. is narrow, and does not possess the 
contours necessary for the storage of a large body of flood-water. 

The Tinselburn and Plankburn, both of which enter the Roaring Meg above 2,000 ft., open out into 
large basins that could easily be converted into impounding dams by the blocking of their narrow gorge- 
like outlets that are cut through the ridge of rock separating the Meg from the old coal-basin. 

The water of the Roaring Meg is an asset of great value to the Cromwell district ; and the water 
may be utilised in different ways. 

The intake could be placed at, say, 300 ft. above the Kawarau, and the water piped down the gorge 
to the Cromwell Flat. Besides using the water for the primary pujpose of irrigation, each farmer with 
evfen half a sluice-head would be able to develop all the energy required for milUng, chaff-cutting, and 
general farm purposes, leaving the spent water still available for irrigation. 

* A New Zealand Government sluice-head is equal to a flow of 1 cubic foot of water per second. 




^. 



CJ 



-J 










23 

Or the stream could be tapped at, say, 2,200 ft. and the water piped to the Kawarau River at Hen- 
derson's, where it could be utilised to drive centrifugal pumps placed on the Pelton- wheel shafts, and 
arranged in one or two units. A flow of 15 sluice-heads of water falling 1,000 ft. would develop enough 
power on the Peltons to raise 45 sluice-heads a height of 200 ft. The water so raised could then be 
flumed or piped to Cromwell Flat. 

Or the above scheme could be modified by carrying the high-pressure water to the lower end of the 
gorge and erecting the pimiping-station there. 

Or the high-pressure water could be piped to some convenient station at the lower end of the Kawa- 
rau Gorge, as in the last scheme, and a portion of it used for lifting water by pumping and another por- 
tion used for developing electric energy for dredging and other purposes, the hydro- electric unit being 
so arranged that the spent water could be utihsed for irrigation. 

Climate. 

The Cromwell district possesses a dry salubrious climate with a proportion of sunshine not exceeded 
by any other part of New Zealand. 

The spring and summer are dry, sunny, and windy ; the winter and autumn cold, dry, sunny, 
and bracing. The rainfall is extremely low for New Zealand, ranging from 12 in. to 15 in. a year. 

Vegetation. 

The Cromwiill terraces and Clutha flats, notivithstandiug the drifting sand and sand-storms so pre- 
valent in spring and early summer, are covered with strong tussock. 

The mountain-tops are carpeted with a variety of native grasses, while Senecios, Celmisias, butter- 
cups, and the patch plants usually found in these alpine and subalpine regions are Abundant. In a few 
sheltered gulhes there are a few ragged bushes of the thorny wild-Irishman or matakauri, and on the 
high tops a variety of stunted Veronica. 

Forest vegetation is entirely absent, but there is ex-idence that this was not always so. Above the 
2,000 ft. contour of Mount Malcolm and Mount Hocken there are still many logs of totara (Podocarpus 
totara), charred and well preserved, lying on the surface of the ground. The older settlers state that 
totara logs were at one time common on the Dunstan, Pisa, Carrick, and Remarkable Mountains, and 
proved of great value to the early pioneers for fuel and fencing purposes. 

The totara forests apparently flourished above the flood-level of the Pleistocene rivers that filled 
the old lake-basins. They were probably destroyed by fire. 



24 



CHAPTER III. 



GENERAL GEOLOGY. 





Page 








Page 


Table of Formations 


. 24 


Kakanui Series — continued. 


Maniototo Series 


. 24 


Thickness . . . . . . . . 30 


Distribution . . 


. 24 


Relation to Underlying Formation 


. 30 


Rocks 


. 24 


Relation to Overlying Formation 


. 30 


Disposition of Strata . . 


. 25 


Age 




. 30 


Foliation 


. 25 


Eruptive Rocks 






. 31 


Thickness 


. 25 


Economic Minerals 






. 31 


Origin of Schists 


. 25 


i'liocene (Lacustrine Sen 


es) 




. 31 


Dynamiciil Origin of Metamorphism 


. 25 


Cromwell Section 






. 31 


Relation to Underlying Formation 


. 27 


Bannockburn Section 






. 31 


Age 


. 28 


Pleistocene 






. 33 


Eruptive Rocks 


. 28 


Morainic Matter 






. 33 


Economic ilinerals 


. 29 


High-level Gravels 






. 33 


Kakanui Series . . 


. 30 


Modified Glacier Drift 






. 34 


Distribution . . 


. 30 


Terrace Gravels 






. 34 


Rocks 


. 30 


Recent 






. 35 



The geological formations represented in the district are sliowTi below in tabulated form in the order 
nf their age and superposition : — 

Table of _^ORMATIO,^£. 
Recent — 

River-beds, sandhills, swamps, &c. 
Pleistocene — 

a. Terrace gravels, modified glacier drift, old fans. 

h. High-level terrace gravels and glacier moraines. 
Pliocene (Lacustrine Series) — 

a. Sandstone gravels. 

h. Quartz drifts. 

c. Sands, clays, and lignite. 
Palseozoic — 

Kakanui Series — 

a. Mica-schist, altered gr.ywacke and mudstones. 

Maniototo Series — 

a. IVIica-schist and chlorite-schist. 
Igneous — 

Serpentine dyke in mica-scliist. 



Maniototo Series. 

Distribution. — This formation occupies the whole of the Wakefield, Cromwell, Crown, and Kawarau 
Survey Districts, and the greater part of Baimockbuni District. It is prominently developed in the 
Dimstan, Pisa, and Crown Ranges, and occupies the summit of the Carrick Range. 

Rocks. — It is composed mainly of mica-schist, iu which sometimes the quartz and sometimes the 
mica is the more largely developed, but the former generally predominates. Ordinarily the mica is 
sericitic muscovite of a silverj'-grey colour. The quartz is commonly greyish-white, with sometimes 
a bluish tinge. 

Many bands of chlorite-schist occur in the mica-schist. They are well seen in the lower Kawarau 
Gorge, and on Pisa Range, also at the upper end of the Kawarau Gorge above Gibbston, and along 
the Arrow River between Arrowtown and Soho jimction. 



25 

The chlorite-schist often contains a large quantity of magnetite, which occurs as large and small 
aggregates, and in well-developed octahedra. The band of chlorite-schist which traverses the summit 
of Pisa Range contains nests and grains of specular iron. The chloritoid mica-schist does not contain 
much visible magnetite. This is the source of the. black sand found in the gold drifts. 

In most places the mica-schist is sharply plicated, and where liighly micaceous it possesses a wavy 
corrugated structure. 

In some places, but most often in the neighbourhood of the chlorite-schist bands, the mica-schist 
passes into a micaceous quartz-schist. In other places the mica-schist contains a good deal of chlorite, 
forming a chloritoid mica-schist. It is noticeable that where most argillaceous the schists are the most 
altered. 

Towards the higher part of the series the schists become less altered, and pass almost imperceptibly 
into partially altered argillaceous and arenaceous micaceous rocks, foliated with quartz laminae that 
conunonly form more continuous sheets than the laminae in the highly altered schists, which are always 
more or less lenticular in form. 

Disposition of Strata. — On the summit of Dmistan Range the scliists are l}ing nearly horizontal ; 
but on descending towards the Dunstau Gorge the angle of dip gradually increases, so that at the gorge, 
as, for example, near the mouth of Sonora Creek, they are nearly vertical. From the gorge towards 
Cairnmuir the inclination once more gradually flattens imtil it becomes nearly horizontal on the crest 
of that mountain. 

Along the flanks of the Carrick Range the strata stand almost vertical, dipping tirst east for a 
short distance and then west. The westerly dip is continued to the summit of the mountain, where 
the rocks lie almost quite flat. 

The strata are highly .nclined along the eastern side of Pisa Range, and often much disturbed, 
especially near the zone of faulting. Outside of this zone the dip is towards the west or north-west 
at high angles until the top of the range is reached, beyond which the angle gradually flattens until 
at the Roaring Meg it is about 30°. 

From Arrowtown to Soho the strata dip westerly with great regularity, at angles varj^iug from 
45° to 60°. 

Foliation. — The changes in lithological character of the rocks coincide with the plane of foliation, 
from which it follows that the fohation coincides with the bedding-plane of the original sediments. 
Moreover, the plane of foliation dips towards that portion of the Kakanui schists that lies ixearest. 

Thickness. — The greatest observed thickness of the Maniototo Series in the Alexandra district 
was 10,000 ft. In the Cromwell district it does not exceed 12,000 ft ; but going westward there is a 
remarkable increase in thickness. In the section along the Arrow and Soho the schists cannot be less 
than 30,000 ft. thick, and this increase is not confined to the mica-schist alone. The bands of chlorite- 
schist. which in the Wakefield district have an aggregate thickness of some 250 ft., widen out con- 
siderably near the Soho jmiction. 

The infolding of two parallel belts of lacustrine coal-measures at the Roaring Meg and Gibbston, 
the difEerent elevations at which the measures occur along these belts, and the apparent enormous 
thickening of the schists going westward seem to point to the existence of extensive isocUnal folding 
between the Roaring Meg and Soho. 

Origin of the Schists. — The examination of the schists both in the field and in the laboratory 
leaves httle doubt that the mica-schist is composed of altered argillaceous and arenaceous sedi- 
ments, and the chlorite schist of altered basic volcanics of contemporary date. 

Dynamical Origin of Metamorphism. — The Maniototian schists, over an area of more than five 
thousand square miles and through a thickness of several miles of material, have been subjected to a 
remarkable degree of metamorphism. A striking feature of this metamorphism is its wonderful 
uniformity. And a perhaps no less striking feature is the almost complete absence of intrusive sills 
or dykes throughout the length and breadth of this great schistose area. 

The deformation causid by lateral compression on alternating weak and strong layers is 
beautifully illustrated in all parts of the Maniototian. Thus the weaker zones are more closely 
plicated than the stronger : and in the softer layers that are controlled by stronger bands we 



26 

have conspicuous examples of rock-flowage, more particularly in the spaces lying between the apices 
of the plications. 

In the belts of tensional stres the foliation of the stronger beds is often crossed by small diagonal 
rents, now filled with secondary quartz. In the zones of compressive stress the softer layers have 
been compacted, while the stronger beds have been puckered into small folds whose axes he at right 
angles to the line of force . Plate V shows a faulted vein of quartz that has been puckered in this way. 

The metamorphism must be mainly dynamical. The extensive regional alteration, the absence 
of igneous intrusions, the intense plication, and the many evidences of tensional and lateral strain, 
all tend to confirm this conclusion. Moreover, the intensity of metamorphism is always proportional to 
the stratigraphic deformation. 

Sills and batholiths might conceivably exist in this area at some distance below the surface ; but 
if they do exist it is inconceivable that they should be present in such dimension as to cause thermal 
metamorphism of such a regional character as that presente i to us in eastern and central Otago. 

If we assume, as seems a warrantable deduction from the geologic evidence, that the metamor- 
phism is dynamical we must offer some explanation of the origin of the dynamic forces. And here we 
are faced with many difficulties. 

In a great belt ninety miles long, extending from the sea to the foot of the main divide, and fifty 
miles wide these highly metamorphosed schists are perfectly undisturbed, being commonJy horizontal 
or gently undulating, except along the flanks of the great block moxintains, where, as already described, 
they are locally tilted at high angles along the lines of major dislocation, like the sides of an inverted 
pudding-dish. 

In this area, which is free from tectonic folding, we have all the e^'idences of intense compression 
that are usually seen in a highly involved and closely folded complex of crystalline rocks. 

The conception that these piles of flat-lying highly altered schist are the ruins of great recum- 
bent folds not unnaturally presents itself to the mind ; but on closer examination it is found that the 
stratigraphic relations of the conformably overlying semi-schistose Kakanuian and succeeding rocks 
do not offer any support to this view. 

It cannot be asserted that the schists have occupied the same horizontal position ever since the 
deposition of the materials of which they^were formed in the middle or lower Palaeozoic, but we have 
at least evidence that they were lying in the same^undisturbed position at the close of the Eocene. 
Thus, along the east coast of Otago horizontal Miocene Tertiaries of the Oamaru Series rest directly 
on the deeply eroded but horizontal schists of the Maniototian. 

Tectonic mountains are merely a manifestation of the relief of crustal stresses afforded by bending 
and folding. In this region we have no tectonic mountains, but only great table-topped block moun- 
tains in a wonderful state of preservation, and separated from each other by deep basins or graben that 
are linked up by rift gorges and valleys of erosion of post-Phocene date. 

The stresses in the upper stratum of the crust are compressive, in the lower tensional. The 
former, being gravitational will create stresses acting in two directions — namely, vertical, shear, acting 
towards the centre of the earth ; and horizontal shear, tending to make the crustal component layers 
slide over each other. 

In the lower stratum the tensional stresses tend to find relief by uplift. But since the tensional 
stresses and horizontal shear are tangical and act in the same direction they wiU unite their forces to 
cause upUft. 

Where the forces of uphft balance those of subsidence there will be jrustal equilibriimi ; but it is 
inconceivable that such nice adjustment could ever be estabhshed, or, if estab ished, that it could be 
maintained for long, except perhaps in pelagic depths. In continental areas, where the migration of 
crustal matter is comparatively great, the crustal balance will be more subject to disturbance than 
elsewhere. 

The tension on the lower side of the crust will tend to cause rupture, and where fractures are 
formed they will be filled with magmatic injections. Tlie first effect of these injections will be to 
intensify the tensional stresses ; but afterwards, when cooled, they will be resistant, acting the part of 
a keystone in an arch. 



PLATI-: V 




IJoLI.DKH SHOWlNc; A FaLI.TKD VkI.N ok (^LAliTZ THAT HAS HKKN I'UCKKKKD Willi.]; 
THE ENCLOSING AltEHED GhEYWACKE HAS BEEN COMPHESSED. 



liidktin .\<>. /j.j 



[To fac'e p. 2'6. 



Tb accompcuiy BidleUn N° 5, Cromv/ell SiihcbivistonWestern, Otago J)ivision 



GEOLOGICAL MAP OF 



Geological Reference 



RECENT _ _ RrverBeds. Loess. 



PL£ieTOCENC< 




28 

In the region lying between the Hiddei' Falls Creek and Red Hill, inland of Awarua (Big) Bav, 
the mica-schists abut against the Te Anau Series, which consists of dun.ite, serpentine, and lime- 
stone, associated with the green sandstones and breccias so characteristic of this formation. 

The junction between the two formations is a sharply defined fault-line, and, so far as the strati- 
graphical evidence goes, the Te Anau Series appears to underlie the mica- schist. 

Age. — The Mauiototo Series of highly altered mica schist contains no internal evidence of its age. 
Sir James Hector* in 1875 considered the foliated schists of Otago as Upper Silurian, and in 1886, 
Siluriau,| or even younger. 

In 1875 Captain HuttonJ placed them in the Silurian, but in 1891 he reviewed his former opinion 
and placed them in the Arch8ean.§ 

In 1902 the wTiter|| placed these schists in the Silurian. 

The highly altered mica-schist passes upward into the less-altered argillaceous and arenaceous 
rocks of the Kakanui Series, but the line of demarcation is purely empirical and often difficult 
to define. 

The Kakanui Series in its turn passes upward into less and less altered rocks, until at last we reach 
mudstones, sandstones, and conglomerates containing fossils that are believed to be Permian or Permo- 
Carboniferous,^ but may be younger. These latter are the Mount St. Mary beds described by the 
writer in 1903. 

Between the Waitaki Eiver and Mount St. Mary, outside the limits of the Cromwell subdivision 
there is a continuous succession of strata from the grey silky phyllites at the base to the unaltered 
mudstones and sandstones near the top of Mount St. Mary. The dip is always to the south- 
west. 

On the Manuherikia side the foliated schist passes upward without a break in the succession into 
mudstones and sandstones that, judging alone from their lithological character, might be the Jurassic 
or Triassic rocks of Wellington. This transition is well seen near St. Bathan's. and in the ridge 
near Hill's Creek connecting Blackstone Hill with the Hawkdun Mountains, and also at Wedder- 
burn. 

The Mount St. Mary section is in the direct line of Hill's Creek section, but there is a gap 
of twelve miles between the Hawkdun Range and Mount St. Mary still to be traversed in order to 
link up the two sections. 

The south-west dip at Mount St. Mary and the north-east dip at Hawkdun Range indicate that 
the strata in the unexplored gap are arranged as a shallow synclinal or in a series of gentle folds. 

This is the first positive evidence we have found deahng with the age of the Otago schists, and its 
tendency is to show that they are of less antiquity than hitherto supposed. 

Until the gap between the Hawkdun Range and Mount St. Mary is bridged it would be premature 
to ascribe the foliated Maniototian schists to any particular age, but from the evidence already avail- 
able the writer does not think it probable that they will be found to be older than Carboniferous or 
Devonian. 

Eruptive Rocks. — Only one occurrence of igneous rock was found in the district. Near the source 
of the Springburn, a branch of the Gentle Annie, there is a dyke of serpentine \\'ith an exposure half 
a mile long and from 3 to 5 chains wide. 

At one point near the old asbestos workings, the actual contact between the mica-schist and ser- 
pentine is very clearly exposed in a steep face. The schist, which elsewhere in this neighbourhood 
is soft, friable, and crumbling, is at the contact baked into a brittle, sintery, or porcellanite-like rock 
in which the original quartz laminae are clearly defined. This contact-rock is fighter in colour than the 
original schist, and possesses a dry brick-like feel. 

The schist along the contact varies from a pale-green chloritic mica-schist to a bluish-grey silky 
mica-schist, often approaching a phylfite in general character and appearance 



♦Hector: Quart. Jour. Geol. Soc, 1865, vol. xxi, p. 128. f Hector : "Outline of New Zealand Geology," 

1886, p. 83. JHutton: "Geology of Otago," 1875, p. 32; and Quart. Jour. Geol. Soc, 1885, vol. xli, p. 194. 

§Hutton: Trans. N.Z. Inst., 1891, vol. xxiv, p. 358. ||Park: Trans. N.Z. Inst., 1902, vol. xxxv, p. 391. 

TfPark: Trans. N.Z. Inst., vol. xxxvi, 1903, p. 447. 



29 

Along the north-eastern boundary of the dyke, there occur in the chloritic mica-schist small lenses 
and bundles of pale-green actinolite. 

On the opposite side of the dyke — that is, along the south-west contact — the mica-schist, as seen 
at the lower end of the igneous intrusion, is altered into a gneiss-like rock, in which flakes of biotite 
are strongly deve'oped. The flakes of biotite do not lie parallel with the foliation, but are disposed 
at right angles to it : and the transverse sections of the flakes being also at right angles to the rock- 
folia?, a somewhat remarkable graphic appearance is imparted to the rock. 

The alteration of the schists and the production of actinolite and biotite at the contact are 
effects of intense thermal metamorphism. 

The origin of the actinolite along the north-east contact is directly traceable to the alteration 
of the chloritic matter in the mica -schist ; but at the other contact, where chloritic matter is feebly 
represented and the secondary biotite abundant, the view that there has been a migration of 
some of the ferro-magnesian constituents from the intrusive magma before cooling took place 
does not seem opposed to the facts, although difficult of proof without an exhaustive chemical 
investigation. 

The serpentine near the eastern contact contains irregular veins and bunches of asbestos, veins 
of calcite, and nests of talc. The asbestos is of inferior quality and patchy. 

The original rock from which the serpentine was derived is not apparent. That it was some ultra- 
basic igneous rock, such as olivine, is. however, certain. 

This serpentine dyke is somewhat remarkable in that it is the only occurrence of an igneous rock 
in the Cromwell district. 

Captain Hutton and Professor Ulrich, in their book o!i " The Geology of Otago and Southland," 
1875, refer to an igneous dyke in the Carrick Range. 

The former says, " I know but one small dyke of porphvrite in the Carrick Ranges " (p. 31). This 
is the only reference Hutton makes tf) the dyke either in the above work or in his subsequent WTitings 
dealing with the schists of Otago. 

Professor Ulrich is somewhat more definite. On page 157 he says, " Only at two places within 
the extensive metamorphic district I obtained evidence of the existence of an intrusive dyke — viz., 
high up on the Carrick Range, in small dyke- and knob-Hke protrusions of a dark ' horn.stonc porphyry,' 
and at Alexandra in several specimens of a similar porph^TV said to be derived from a reef-like out- 
crop (no doubt a dyke) on the northern slopes of the Old Man Range." 

A careful search of the Carrick Range in the place indicated failed to locate the dyke spoken of 
by Hutton and Ulrich. Near Carric-ktown, however, several dyke-like outcrops were found, locally 
known to the miners as " dykes." They are not dykes, but outcrops of hard, bluish-grey, flintv 
or horny quartz, often much slickensided on one wall. 

Singularly enoiigh, outcrops of similar dense horny quartz veins are known on the Old Man Range 
and along the east side of the Manuherilda Valley near Alexandra. 



Springbw" 




Flo. 9. Section across Sekpentink Octceop at Asbestos Mine, Spbingburn. 
a. Mica-schist, chloritic. b. Mica-schist, almost a phyllite. c. Serpentine. 



Economic Minerals. — This formation contains gold-bearing veins at Bendigo and Carrick Range, 
which at one time yielded a large output of gold. Besides gold, the lower schists contain veins of anti- 
mony and scheeUte, to which reference will be found in Chapter IV. 



30 

Kakancti Series. 

Distribution. — The rocks of this series occupy the lower flank of Carrick Range, the floor of 
Bannockburn Vallf y, and the summit of the Remarkables from Doolan's Creek to Double Cove. 

Rocks. — These generally consist of partiilly altered rrgillaceoi s and arenaceous ro^ks 1; minated 
with quartz, and often veined with strings of quartz, fhey are sometimes puckered and pUcated, 
but less often than the lower schists. 

Bands of mica-schist also occur in them at intervals, and occasionally layers of greenish chloritoid 
schist. The chloritic bands seldom or never contain visible magnetite, a'^feature which distinguishes 
them from the chlorite-schist bands of the Maniototian. The occurrence of the mica-schist makes it 
somewhat difficult to define the boundary between the two divisions. The extremes are easil^c- recognis- 
able ; the means less easily. The two formations are, however, easily recognisable in the field. 

In the upper part of the series the rocks become slaty and flaggy and less quartzose, in places 
passing into mudstones and grewackes that show little or no trace of mctamorphism. 

In some places these rocks are traversed by many parallel thin veins of quartz, lying at angles 
varying from 20° to 35° to the plane of the foliation. These inclined veins are very tm.iform in thick- 
ness and inclination over large areas of rock. They do not displace the quartz laminae of the main 
foliation, and appear to represent a secondary but less pronounced plane of foliation induced in the 
rock about the time of the main foliation, which is in all cases parallel to the original bedding. 

Thickness. — The greatest area covered by these rocks is on the range extending from Gibbston 
coal-mine to Double Cone on the Remarkables. Here they lie at comparatively flat angles, and do not 
represent a great thickness of strata, probably not more than 5,000 ft. within the limits of the area 
covered by this report. 

The Bannockburn area of these rocks occurs infolded in a closed syncline, which has in a large 
measure preserved them from destruction. The thickness exposed here does not exceed 4,000 ft. 

Relation to Underlying Formation. — The rocks included in this division are merely the upper 
portion of the great series of metamorphic sedimentary rocks in Central Otago. In the Alexandra 
district they are typically exposed in the hills and gullies on the left side of the Manuherikia River, 
immediately opposite the Town of Alexandra and quite near the river-jimction. 

In the Cromwell district they are best seen on the ridge that separates the Bannockburn Stream from 
the old workings at Bannockburn Diggings. This ridge starts at the bridge over the Kawaraii, where 
the rocks are distinctly chloritoid, and runs southward in a course almost parallel with the lower reaches 
of the Bannockburn. It is cut through by Shepherd's Creek and by an old watercourse below Horn's 
store at Bannockburn, and in both places the rocks are conveniently situated for close investigation. 

Relation to Overlying Formation. — As already stated, the rocks exposed at Baimockbum are merely 
an infolded remnant of the upper schists : and in the absence of overlying rocks belonging to the same 
stratigraphical succession, or of a formation of greater age than the Pliocene coal strata which lie on 
their upturned edges, nothing can be f oimd bearing on their probable age in the Cromwell district. 

The upper schists in the area between the Kawarau and Remarkables dip away to the south-west, 
and pass outside our boundary without disclosing the upper members of the series. 

But in the upper part of the Manuherikia basin, in the Blackstone Hill Range and its continuation, 
and in the low undulating ridges near Hill's Creek, there is a continuous succession of strata from the 
lower highly altered contorted mica-schist up to partially altered schists, which are often slaty and 
arenaceous with a flaggy structure. These last pass upwards by an almost insensible gradation to 
jointed mudstones and grewacke with beds of conglomerate, the former being well exposed at St. 
Bathan s and on th e saddle near Hill's Creek on the main coach-road from Rough -l dge to St. Bathan's. 

Age. — -On the Waitaki side of the Hawkd ;n Range the same succession o; rocks is exposed, the 
mica-schist being followed by partially altered rocks, which pass upward into mudstones and grev- 
wacke with beds of conglomerate. 

At Moimt St. Mary the unaltered rocks are richly fossiliferous, and the fossils are belie -ed to indi- 
cate an age somewhere between Permian* and Permo-Carboniferous.f The strata dip towards the 

♦McKay: N.Z. Geol. Sur. Reports of Explorations, 1881, p. 77. f Park : Trans. N.Z. Inst., vol. xxxvi, 1904, p. 447. 



To accompiabv Jiidleiin TV" J", Cruinwcll SiihdiAistonWestem Otaqo Division. 



Green Valley Ck: Devil s Ck 



Tri^ U 



Dunstan Mountains 

S-fOO' 



Fault 




Section alon^ Line A B, Wakefield Survey District 



Queensberry Hill 

S03S' 



Roaring Me^ Creek 
Fault 



Pisa Range^ Fault 



Lowburn Strafford Gully 




Section along Line AA,Cromwell Survey District 



Mount Difficulty Double Rock 

I ,^ „. ^°^^ 

I Kawarau River 

Fault 




Section along Line BB, Cromwell Survey District 



Mount Edward 



Kawarau River 



Carrick Range 
Trig A 



Shepherd Creek 
Fault 




Trig N 

Tucker Gully r, , , 

f '\ ' tSannockbu 



Section along Line AA, Kawarau Survey District 



Section along Line AA, Bannockburn Survey District 



Mount Ramsay 
■jooo' 



Cowcliff Hill Whitecliff 

iKawarau River 



Quartz Knoll 





Section along Line BB, Crown and Kawarau Survey District 
Reference to Geological Colours 



RECENT 



PLEISTOCENE 



PLIOCENE 
Manuherikia Series 



JAMES MACKINTOSH BELL 
DIRECTOR 



f 




\ 


y/'';'{f-. 




' Q->Q O ^ 



PALEOZOIC 

Kakanui Maniototo 

Series Series 



Serpervtine Dyke. loees River Terraces Mqh-lmel TermceB Sandstone Gravels Oays^Sands ShaZes Clays QuM.rt2Jhi.ft Upper Schists Lower Schists 

Asbestos River Bedjs ModiAed Glacial PriA. Glacial Drift {Maori Bottom.) WithLi^ite S,liynlte (GrarUteWash) 



Scale of Cliaiiis 



I J^^aHTi by OA Darhy Se^t 07 



so 60 40 20 

|- ' I I I 



31 

Hawkdim Range. Thiis on both sides of this range we have a similar succession of strata, each dipping 
to the other. A gap of twelve miles in a straight line separates the two observed points. The inter- 
v(nin;,' space has been mapped by Mr. A. McKay as being occupied by unaltered rocks, which he refers 
to the Wairoa. Kaihiku, Maitai, and Te Anau Series.* The gap that still remains to be explored is 
drained by the Otamatakau River, which drains into the Waitaki. 

If a direct relationship is traced between the Waitaki and Manuherikia sections, as we have reason 
to believe will be the case, we shall be compelled to refer the Kakanui schists to the upper part of the 
Carboniferous period. 

Eruptive Rocks. — No eruptive rocks are known in association with the Kakanui Series in this 
part of Cential Otago. The chloritic bands are probably altered contemporary volcanics. 

Economic Minerals. — In Hawkesbum Creek the slaty schists contain a deposit of impure graphite, 
the extent of which is not known. Veins of quartz are abimdant in this series, but so far none of them 
have proved of economic value. 

Pliocene (Lacustrine Series). 

a. Sandstone gravels (Maori bottom). 

b. Quartz drifts. 

c. Sands, clay, and lignite. 

On the Cromwell side of the Cromwell basin the lower members only are present. They dip 
away from the schist towards the centre of the basin at angles that vary from 30° to 35° near 
the outcrop, but gradually flatten in the direction of the dip, as was shown by the coal-mining 
operations near Cromwell. 

On the Pisa side of the basin the beds are tilted at high angles, and dip towards Cromwell or the 
Clutha. 

Near the mouth of Bannockbum Stream the lignite measures lie almost undisturbed, dipping away 
from the schist on the north bank at an angle of 10°. On the opposite bank they stand at very high 
angles, having been abruptly dislocated by a fault which runs nearly parallel with the lower end of the 
stream. 

In the old Bannockbum basin, lying between the Post Office and the Carrick Range, the measures 
are disposed in a syncline, on the Carrick Range side of which they are tilted on end along the course 
of the great fault. 

Cromwell Section. — The lignitic series of lacustrine beds crops out along the bank of the Kawarau, 
extending from the Chinese camp at Cromwell to Bannockbum. The strike of the beds is about 75° 
(true), and this course seems to be maintained pretty uniformly throughout. 

The dip is towards the west. The angle of dip, as disclosed at the outcrops nearest Cromwell, 
varies from 20° to 30°, the variation being apparently due to outcrop-curvature. 

The lowest bed is exposed on the bank of the river at the Chinese camp. It is (1) a greyish- white 
plastic clay, locally known as " pipeclay." The actual thickness of this stratum is not known, but 
judging from the distance to the schist basement rock near-by, it cannot be less than 40 ft. or 50 ft. 
The clay in its upper part is interbedded with thin layers of angular quartz grit. This quartz grit is 
the " granite wash " of the miners at Tinkers and St. Bathan's, and occupies the same position 
in the lacustrine series as does the gold-bearing quartz wash at these places. 

The pipeclay is followed by (2) a bed of dark-grey, almost black, micaceous shale, of which there 
is a visible thickness of some 12 ft. or 14 ft. 

Then follows (3) a bed of soft, yellowish sand, of a fine and uniform texture, about 8 ft. or 10 ft. 
thick. 

After this, still passing along the bank of the river, there comes (4) a bed of gritty quartz drift, 
15 ft. thick, showing current bedding. This bed is fairly compact, but not in any way indurated. 

* McKay : N.Z. Geol. Sur. Reporte of Explorations, 1881, p. 77. 



32 



Overlying the quartz drift (5) there is a bed of yellow to paile-bufP or drab-coloured shales, some 20 ft. 
or more thick. These shales are very fissile, breaking readily into very thin sheets. About the middle 
of the bed they contain numerous well-preserved leaf-impressions, mostly those of dicotylidonous 
plants and ferns. In one layer there are th':' remains of a mussel, very much flattened. This shell 
appears to be the same as that found in the shales at the base of the lignitic measures at Dairy Creek, 
near Clyde. 

Following the bufi shales is a bed (6) of some 20 ft. of fireclay, which is in turn followed by (7) a 
seam of somewhat impure lignite about -5 ft. thick. After the lignite there comes (8) a bed of soft 
sandstone of unknown thickness in this Une of section. 

The beds enumerated above strike nearly parallel with the course of the Kawarau, and hence in pass- 
ing along the bank are exposed in due sequence, beginning with the lowest beds at the Chinese camp. 

About a quarter of a mile above the Chinese camp there is a tail-race cut in the lacustrine beds. 
It runs nearly at right angles to the strike, and exposes a section that cannot fail to be instructive when 
boring for lignite is undertaken in other parts of the basin. The lowest members of the series are not 
exposed here. The shales (6) forming the first bed, clearly seen at the end of the tail-race, appear to 
correspond to the buff-coloured shales (5) cropping out on the bank of the river at the Chinese camp. 

The succession of beds, beginning at the bottom, is as follows : — 

a. Obscure . . . . . . . . . . . . . . . . 35 

b. Drab-coloured micaceous shales . . . . . . . . . . 5 

c. Fireclay . . . . . . . . . . . . . . . 7*5 

d. Lignite and carbonaceous shale . . . . . . . . . . 11 

e. Firec'ay with leaf -impressions . . . . . . . . . . 5 

/. Dark-drab carbonaceous shak . . . . . . . . . . 6*5 

g. Clays with leaf-impressions . . . . . . . . . . 3 

h. Yellowish-brown sand and soft micaceous sandstone . . . . . . 24 

{. Micaceous sandy clay . . . . . . . . . . . 8 

j. Clay with hard concretions . . . . . . . . . . 2 

Tc. Fireclay . . . . . . . . . . . . . . . . 4*5 

I. Impure lignite . . . . . . . . . . . . . . 1 "5 

m. Grey fissile shales . . . . . . . . . . . 4 

n. Soft micaceous sandstone . . . . . . . . . . . . 70 

0. Clays with black carbonaceous band at top . . . . . . . . 8*5 

f. Fine-grained micaceous sandstone . . . . , . . . . . 30 

q. Seam of impure lignite . . . . . . . . . . * . . 2 

r. Clay and sandy beds (exposed) . . . . . . . . . . 11 



Total exposed 

The above succession is shown in the section facing this page. 



238-5 



Bannockburn Section. — At Bannockburn, where a good section of the lacustrine series is exposed 
on the floor of the old alluvial claims where the overlying schistose river-gravels have been sluiced 
away, the succession of beds is as under, beginning at the base of the series : — 

1. Quartz grits with hard, brown, flaggy layers cemented by peroxide of iron. 

2. Sands and clays. 

3. BufE-coloured fissile shales with leaf -impressions and casts of mussels much flattened. 

4. Sands and clays with seams of lignite. 

5. Clays and sands. 

6. Soft sandstone. 

7. Sandy clays. 

8. Clays, sands, and soft sandstones alternating with white quartz grits. 

9. Soft sandstones. 



o 



d 



.0 



t 



0- 






^ 



V' 



■IJ.J.JJ 




J.0 f^sf uo suiof 




0) 

E 
o 

1. 

O 

E 

CD 

o 

(U 
CD 
(U 

C 

o 

1- 
(0 
CD 

c 

CD 
O 

CO 

'cD 
-P 

"OO 

c 

c 
o 



38 

The total thickness is between 500 ft. and 600 ft. Beds 6 to 9, which represent a considerable 
thickness, are not seen in the Cromwell section. On the other hand, the sandstone gravels — the " Maori 
bottom " of allu\aal miners — although present at Quartz Reef Point and between the Hospital and 
Five-mile Creek, are absent at Baimockburn. 

These sandstone gravels form the high terraces which extend from the back of Cromwell Flat along 
the foot of Pisa Range to the boundary of Wakefield Survey District. They are covered with Pleisto- 
cene gravels, which in most places occur as a thin sujierficial layer lying on the top and slopes of 
the terraces. 

The cement stones, or " Chinamen " of the miners, occur in the basin, but are never abundant. 
They are perhaps more common on the slopes of Cairnmuir and Bamiockburn Valley than elsewhere. 

They are portions of the quartz sands and grits of the lignitic series that have been cemented into 
a hard rock by siliceous waters issuing from the schists on which they rested at the time of their 
deposition. 

Pleistocene. 

a. Terrace gravels, modified glacier drift, old fans. 
h. High-level terrace gravels and glacier-moraines. 

Morainic Matter. — The remains of an old moraine occur at the end of the Kawarau Gorge, about 
three miles from Cromwell. It consists of angular masses of schist, some of them of enormous size, 
mingled with fluviatile debris. In some places it reaches a height of 300 ft. above the present bed of 
the river. 

The Victoria moraine occupies the floor of the basin between Victoria Bridge and Nevis BlufE. 
Like the Kawarau moraine, it has suffered considerably from the action of the river since its formation, 
ha^^ng been scoured out on the river-edge into a precipice a hundred feet high and levelled on the top 
into what is now a fairly flat terrace. 

A good deal of morainic matter is scattered on the terrace bounding the Kawarau at Gibbston, 
and masses of ice-carried material can be seen in almost all parts of the Cromwell basin ; but, generally 
speaking, the amount of glacier-debris seems relatively small compared with the evidences of ice erosion 
which are everywhere present on the mountain-slopes. 

High-level Gravels. — These occur as a superficial covering on the high terraces on the Pisa side of 
the Cromwell basin, resting sonietimes on the schists, but generally on the " Maori bottom " or lower 
members of the lacustrine series. They also form the high terraces that extend from the Lindis to 
Bendigo. At one time they formed a continuous teiTace from Bendigo to Cromwell, but the greater 
part of this terrace has been removed by the streams that drain the western slopes of the Dunstan Range. 
At the present time only isolated patches remain, those between Bendigo and Quartz Reef Point resting 
in the schist, those at the last place on the lignite measures, " Maori bottom " and schist, and those 
between Quartz Reef Point and Cromwell mainly on the schist. 

One of the most typical examples of these gravels is that forming the terrace on which the reservoir 
for the domestic water-supply of Cromwell is situated. 

The remains of this old terrace can also be traced around the flanks of Cairnmuir to Baimockburn, 
and thence to the Kawarau Gorge. 

A patch of the same gravels occurs on the right side of the Kawarau, nearly opposite the mouth 
of the Roaring Meg. The high gravel terraces at the mouth of the Nevis and on the neck of land at 
the great bend of the Kawarau at Victoria Bridge are also portions of a high terrace that extended 
through the Gibbston basin to the Crown Terrace and the valley of the Arrow. 

The same gravels occur in the Dunstan Gorge and on the rock benches between Alexandra and 
Bald Hill Flat. They also form terraces on the eastern shore of Lake Wakatipu. 

These gravels generally occur between the 1,000 ft. and 1,200 ft. contours, and mark an ancient 
flood-level that extended down the Kawarau and Clutha to Alexandra and Bald Hill Flat. 

This flood-level followed the contours around the Arrow basin and valley, passed into the upper 
Kawarau Gorge, contoured around Gibbston basin, swept past the Nevis BlufE into Victoria basin, 
3 — Cromwell. 



34 

whence it passed over the uec-k ol land to Waitiri and thence followed down the Kawarau to Cromwell 
basin, which it filled up to the 1,200 ft. contcjur, stretching at this level far up the Clutha and Lindis. 

From Cromwell basin it passed through the narrow Dunstan Gorge to the Manuherikia basin, where 
its remains can still be seen spreading out as a great fan from the point of emergence at Clyde to Spring- 
vale on the east and to Butcher's Gully on the south. 

The isolated patches of gravel perched high up in the valley of the Arrow, and found on the summit 
of Crown Terrace, at the mouth of the Nevis, around the Cromwell basin, dowTi the Dunstan Gorge, and 
beyond Alexandra are merely remnants of this ancient flood-level that escaped destruction at the 
time the Kawarau and Clutha Rivers benched and excavated the valleys and basins along their 
courses down to the present contours. 

The most remarkable feature connected with this great high-level flood-plain is the character of 
the gravels and rocky debris of which it is composed. 

The material brought down by the Clutha consisted mainly of well-rounded and waterworn sand- 
stones, greywackes, and quartz, mingled with more or less angular fragments of mica-schist. In this 
drift there is always a small proportion of basalt occurring both as pebbles and large boulders, the latter 
generally found at the highest levels, A few pebbles of pink quartzite are also present. 

The sandstones, grepvacke, basalt, and pink quartzite are foreign to the country between Crom- 
well and Lake Hawea, but occur in situ in the mountain-ranges north and west of that lake. It is 
obvious that these rocks must have been transported across the lake by ice, and this yiew receives 
confirmation from the occurrence of large ice-carried masses of basalt and pink quartzite on the top 
of Clyde moraine. 

After the Clutha glacier retreated to the upper valley, but still spanned the lake, the river picked 
up the ice-borne rocks and rolled them along its bed to the Cromwell basin and Dunstan Gorge, joining 
forces with the Kawarau at the former. 

Turning for a moment to the Kawarau we find that the material contributed to the old flood-level 
by that river consisted mainly of sandstone, greywacke, green breccias, and schist mingled with a small 
proportion of granite, syenite, diorite, and crystalline limestone. These rocks, with the exception of the 
schist, are all foreign to the present watershed of the Kawarau, but are found in situ among the moirn- 
tains on the west side of Lake Wakatipu, and appear to have been ferried over to Queenstown by a 
glacier at the time Lake Wakatipu was bridged by ice. 

These high-level fluvio-glacial gravels have an economic importance from the circumstance that 
they are often gold-bearing, and, although seldom rich enough to pay for sluicing, the rewash of them 
has been very profitable, more especially on the terrace slopes between Lowburn and Five-mile Streams 
and at Quartz Reef Point, where they lie on the " Maori bottom." 

The fluvio-glacial drifts pass downwards into purely fluviatile gravels and sands, which are well 
seen beneath the modified glacier drift along the course of the Kawarau at CromweU, and on the Clutha 
between Cromwell and Deadman's Point. 

Modified Glacier Drift. — This is the drift which has yielded the great bulk of the gold raised in the 
Cromwell district. It occurs on both banks of the Kawarau, extending from the Gorge to Cromwell 
and thence to Deadman's Point. In other words, it follows the present course of the Kawarau and 
Clutha, and occupies an old channel excavated in the fluviatile drifts forming the Cromwell terraces. 

This old channel has sloping sides that reach on each side a distance of several chains back from 
the present river-bed. (See special map of Cromwell facing page 46.) 

The glacier drift consists mainly of gravels and sands, in which occur many large and small angular 
masses of country rock, mostly mica and chlorite-schist. 

In this drift, the writer found near the Chinese camp at Cromwell several large rounded masses of 
shelly limestone containing shells of Ostrea, Venus, and Glycimeris. The parent-rock occurs in the 
Shotover Valley and at Bob's Cove, Lake Wakatipu. W 

At the upper end of Gibbston Flat there Hes a large mass of greyish-white crystalline limestone, a 
rock that does not occur in the present drainage-area of the Kawarau. ! p" [S(S 

Terrace Gravels. — These were formed at the close of the Pleistocene period, some time'^after the 
retreat of the glaciers. 



•'o acjOurripoj-Ly Ji~u2IetinI7^^ S 




Section across Lake beds at Quartzville , 
Smith's Gully 




Section across Lake beds near Pipeclay Gully 



Reference 



Recent CL.ALlicwtcrrv 

Fleistocene hBartruDckbiav^ Schist WasTx' 

\^ e.FossiZtfkroiLS Shales 
Pltocen& \ To. CoaZ Seams 
[ n, . CLcLys 

Paleozoic s. Upper- ScJvLsts 



K. Sccndy ClcLys 
m Shales 
p Qrtts 



GE^j. 



Sy Authoritji John Mai-kay, Goutrnmtnt Printtr, 



To cbccompany SuZletiiL ISP^S 




Section across Lake beds on the 
- Western flank of Round Hill - 



w 




Section across Lake beds near Long Gully 



C, E ff. 



Reference 

FZeistocene h. 3 caxnockbtjurrt Schist IVasTv 

e. FossJlzferotLS STvaZes 
g. SandLs 
K SarLoLy Clays 
rrv. Shdies 



Pliocene 



[? Q 



riTt 



•ir Autlloritt John Maekay. UMtrnmtnl frinfr. 



35 

The gold-bearing gravels at Baimockburn, mainly composed of a creek-shingle in which quartzose 
mica-schist and quartz predominate, the former mostly in flat-shaped pieces, are a typical example of 
the fluviatile debris of this period. 

These gravels are gold-bearing, and a large area of them has been sluiced away in the course of 
mining operations during the past thirty years. 

Recent. 

Under this head are included deposits that are now in course of formation, such as river-beds, river- 
flats, swamps, and drifting sands. 

The drifting sands which have proved so destructive to farming on Cromwell Flat are generally 
believed to have been brought down the Clutha during the great flood of 1878. This would doubtless 
account for a large proportion of the sand, but it should be pointed out that the terrace on which Crom- 
well is built contains a large amount of drift sand mixed with the gravels, and that a constant supply 
of this sand, derived from the terrace-faces between Lowburn and Deadman's Point, is carried by the 
wind across Cromwell Flat. 



3'— Cromwell. 



36 



CHAPTER IV. 



ECONOMIC GEOLOGY. 



Page 



Some Principles of Concentration in River- 




bed Gravels 


36 


Proaress of River Erosion 


3t) 


River-bed Bottom 


37 


Position of Pay-wash . . 


37 


Descent and Arrest of Gold in Travelling 




Drift 


39 


Alluvial Gold . . 


40 


Quartz Drifts 


41 


Sandstone Gravels 


42 


Fluviatile Drifts forming Terraces 


42 


Leads at Quartz Reef Point 


43 


Fluvio-glacial Deposits and Moraines 


44 


Re-sorted Fluvio-glacial Drift . . 


45 


River-bed Gravels and Sands . . 


46 


Crumbling Schist Wash 


46 


The Blowing-down System of Sluicing 


47 


Scope of .System 


47 


The Actual Working . . 


47 


Gold-bearing Lodes 


48 


Bendigo Goldfield 


49 


Cross-lodes 


49 


The Cross-lode . . 


49 


East and West Lodes 


50 


North Lode 


50 


Cromwell Lode 


50 


The South Lode . . 


53 


The Bee Lode 


53 


Hit or Miss Lode 


53 


Aurora Lode 


53 


Anderson's Lode . . 


54 


Lucknow Lode 


54 


Bradford's Lode . . . . . . 


55 


Low-level Adit 


55 


Alta Lode 


55 


Rise and Shine Impregnated Shear Zone 


56 


Genesis of Gold in Shear Zone 


57 


Carrick GoldBeld 


57 


Carrick Gold-bearing Lodes . . 


58 


New Royal Standard No. 1 


58 


New Royal Standard No. 2 


58 



Gold-bearing Lodes — continued. 


Page 


1 Caixick Goldfield — continued. 




Carrick Gold-bearing Lodes — contintied 




CVown and Cross Lode 


. 58 


New Find Lode . . 


. 59 


Caledonia Lode . . 


. 60 


New Caledonia Lode 


. 60 


Carricktown Lodes . . 


. 61 




Elizabeth Lode . . 


. 61 




. Colleen Bawn Lode 


. 61 




Star of the East Lode 


. 61 




The Old Heart of Oak Lode 


. 62 




Black Horse Lode 


. 62 




Pipeclay Gully Lodes 
John Bull Lode . . 


. 62 
. 62 




Robert Burns Lode 


. 62 




Golden Gate Lode 


. 62 




Genesis of Bendigo and Carrick Lodes 


. 63 




Immature Replacement Lodes 
Origin of Minerals 


. 63 
. 63 




Age of Lodes 


. 63 




Position of Pay- ore . . 


. 64 




Secondary Enrichment 


. 64 




Hawksburn Lode 


. 64 




Jolm Bull Quartz Veins 
Lodes in Basin of Roaring Meg . . 
Henderson's Lode . . 


. 65 
. 66 
. 66 




Roaring Meg Veins . . 


. 66 




SUver 


. 66 




Antimony 

Buchan's Lodes 


. 66 
. 67 




Horn's Lode 


. 67 




Asbestos 


. 68 




Graphite 
Coal .. 


. 68 
.. 69 




Excelsior Coal-mine 


.. 69 




Shepherd's Creek Coal-mine 
Roaring Meg Coal 


.. 70 
.. 71 




Gibbston Coal-mine 


.. 71 




Cardrona Coal-mine 


.. 72 




Artesian Water in Central Otago 


.. 73 



Some Principles of Concentration in River-bed Gravels. 

Progress of River Erosion. — The energy of every river is constantly devoted to the wearing-down and 
regrading of its bed ; and this action goes on unceasingly until the channel is worn down to the 
lowest flood-level of the country which may be in some cases the sea, in others an inland lake. 

WTien this is at length effected, the rate of flow is so diminished by the flatness of the gradient 
that the eroding and transporting powers of the river are reduced to a minimum. 

The plane of minimum gradient that will give a perceptible flow towards the sea or lake is termed 
the base-level of the river-system. 

While the trunk river is engaged in the work of grading, and even after this work is completed, 
the primary branches with their secondary and tertiary feeders, down to the smallest streamlet, are 
busily employed in wearing down the land they drain, with the object of reaching the base-level already 
established by the parent river. 

The trunk river naturally finds its base-level in the lower reaches first, and if no land movement 
or disturbance takes place the base-level is slowly carried back until in the course of time all the land 
within the drainage-area is worn down to a surface of low reUef. 



37 

Rivers are found with their base-level in all stages of development, from the turbulent mountain- 
stream to the sluggish river of the plain that is scarce able to carry its load of suspended matter to the 
sea. 

River-bed Bottom. — The gravel drift or wash in a river-bed rests either on the basement rock of the 
district or on clays, clayey sands, partially compacted sand or gravel drift, or other comparatively 
soft matter commonly of late Tertiary date, hnng directly on the bed-rock. * 

The basement rock is known to alluvial miners as " reef bottom " ; and the clays or other material 
interposed between the wash and the bed-rock as " false bottom." 

The " reef bottom " may be slate and sandstone, as in Victoria ; mica-schist, as in Otago ; or granite, 
as in some parts of New South Wales and Queensland. 

There may be alternating stretches of reef and false bottoni in the course of the same river, and 
it will generally be found, as a result of the different geological conditions, that where a false bottom 
exists the channel will be wider and less steep than where a rock bottom occurs. 




22^iles X 



Fio. 10. Longitudinal Section of Kawarau River Bed between the Kawaeau Goroe and Bannockburn 

Bridge 
b. Kawarau Gorge. c. River-wash. d. Upper quartz drifts and clays. e. Lower 
quartz drift. /. Mica-schist. 



a. Bannockburn Bridge. 



In this stretch of river-bed the Kawarau wash rests both on the schist and on the different members 
of the Pliocene lacustrine series, the latter forming a false bottom, that proved very productive. 

Position of Pay-wash. — A river-bed is a natural sludge-chamiel, in which the gold or valuable mineral 
is concentrated into leads or pockets. 

In a river with a steep gradient the gravel wa.sh travels forward very rapidly, fresh supplies being 
continually provided by the erosion of the bed and banks of the stream and its tributaries. 

The wash on the floor of such a river is seldom deep, except in the pot-holes and hollows. In many 
places the bottom may be bare, or covered with only a thin layer of gravel which is continually moving 
onward. 




Fio. U. Showing Wash lying on Rock Bottom of Steep River-bed. 



In a river of moderate velocity the bed is generally covered with a deep layer of travelling drift. 
The wash in a river-bed is always in a state of motion, the greatest movement being in the upper 
layers, and the least at the bottom. 



38 

Besides the onward tendency wliich the whole body of drift possesses, due partly to gravity and 
partly to the flow of water through and over the gravels, the rolling and impact of the upper layers 
as they travel onward cause a vertical motion to be transmitted to the lower layers. 

Particles of gold that find their way into the main channel are first carried forward in the upper 
layer of travelling gravel. As they move forward they are gradually deflected downward by gravity 
until they reach the bottom of the travelKng zone of wash, when they fall rapidly in the almost station- 
ary but vibrating gravel, until they reach the bottom. 

The path of falling particles of gold in a river-drift may be shown diagrammatically as below :— 



Fig. 12. Showing path of Falling Particles of Gold. 



The coarsest particles will fall at a and the finest at h. 

If the channel were straight and of uniform cross-section, and the rate of flow the same in all parts 
of the channel, it is obvious that the particles of gold would tend to fall in a vertical plane only. But 
river-beds are never straight ; and the velocity of flow is not the same at all points of the cross-section, 
being greatest in the middle and least at the sides. As a result of this unequal velocity the gravels 
in the middle of the stream travel faster than the gravels near the sides where there is the greatest 
drag or friction. The tendency of this unequal travel is to throw the heavier particles sideways to- 
wards the banks of the stream. 

The principle underlying this system of concentration is well seen in the use of the miner's pro- 
specting-dish, in which the heavy particles travel inwards towards the vortex or smaller diameter of 
the dish, where the velocity of the moving water is least, while the larger and lighter sands travel 
towards the rim, where the velocity is greatest. 

Take the case of a falUng particle of gold dropped in the middle of a river-bed. Here it is subject 
to two forces — namely, a vertical force due to gravity, and a lateral force due to the unequal travel 
of the gravel wash. The resultant path of these two components is a curve, binding downwards and 
sideways. Before the particle reaches the bottom it may have made sufficient lateral movement to 
enable it to reach the side of the stream, or even to lodge on some ledge or beach on the shelving 
bank. 

But gold is not fed into the middle of rivers. Commonly it is brought in by some side stream 
or comes out of the gravels forming the banks, and hence is soon thrown on to the beaches on one side 
or the other, according to the set of the current. The coarser gold falls first, while the finer particles 
trail down stream for some distance. 

When gold settles in this way on a line of beach or shelving bank it forms what is termed a " lead " 
of gold-wash or pay-wash. It is found, as a matter of experience, that the best gold in a lead is gene- 
rally found not in the deepest part of the gutter, but on the shelving side of the old channel, a result 
doubtless due to the operation of the principle of unequal velocities. 

In accordance with this principle we also find that the richest gold-wash always occurs on the 
inner or concave side of the curves in the course of a river. Of this we have many examples in the 
Kawarau and Dunstan Gorges, and one in the latter may be cited as" a typical occurrence. 



39 

At the Half-way House, the Chitha forms two sharp bends in a distance of some 15 chains. The 
wash at the lower bend, locally known as Golden Point, was very rich. The distribution of the wash 
along the inner side of the curve is well seen in the next fijiure, which is a plan of the river at this 
place. 




Fio. 13. Plan of Clutha River near Half-way Hotse in Divstan Gorce. 
Scale, 8 chains to an inch. 



Goldfscattered throughout the gravels of a river-terrace is partially concentrated in the bottom 
of the gullies intersecting the terrace, but the final concentration takes place in the bed of the trunk 
river draining the district. 

Where the current of the river is rapid only coarse heavy gold will be found on the bottom. The 
bulk of the finer gold will be found in the lower reaches, where the flow is slower. 

The Descent and Arrest of Gold in Travelling Drill. — The horizontal distance through which a par- 
ticle of gold will be carried before it reaches the bottom vnW depend on the rate at which the drift is 
travelling and on the form of the particle. 

The rate of the drift-travel will be governed by the gradient of the bottom and the velocity of 
flow. The greater the velocity of flow, the flatter will be the curve of descent ; and, conversely, the 
slower the rate of flow, the shorter and more convex will be the curve. 

The rate of flow of a stream is mainly dependent on the gradient of the channel-bed, and, neglecting 
the drag due to frictional resistance, is expressed by the formula, — 

But we know that the transporting-power of running water varies as the sixth power of the velocity : 
and in this we see how great must be the influence of velocity of flow in determining the position and 
grade of the mineral concentrates along the course of a stream. 

The classic researches of Kiitter have shown that the depth of the water is also an important function 
of the rate of flow. Thus we find that the velocity and transporting-power of a deep stream, on a given 
gradient, are greater than those of a shallow stream on the same gradient. 

With a given volume of water on a uniform gradient, the velocity will be greatest at the cross- 
sections of least area — that is, in the narrow parts of the channel — and least in the wide reaches of 
greatest sectional area. 

Round, shotty particles of gold will find the bottom quicker than scaly or spongy particles. The 
scaly and bran-like form of river-gold is due to the pounding the particles are subjected to in the 
travelling drift before they reach a resting-place. Such flattened gold may be termed transported 
gold, to distinguish it from rough and shotty gold that has manifestly not travelled far. 



40 

When a particle of gold reaches the bottom it may not at once find a permanent, or even a tempo- 
rary, lodgment. It will continue to move forward until by some lucky^ happening it falls into a cre\dce, 
where it is protected from the scour of the passing drift, or is cast on to a beach in some sheltered 
comer. 

Where one particle of gold can rest imdisturbed, it is obvious that other particles, as well as grains 
and pebbles of magnetite, scheelite, &c., can also find shelter in the same place. In this way leads 
of gold-bearing wash are formed. 

The distance a particle of gold may travel on the bottom before it finds a lodgment wiU depend on 
the ability of the bottom to catch and retain the particle. The power to catch and retain gold will 
depend on the character and arrangement of the bed-rock, the velocity of the stream, the set of the 
current, and the prevalence of floods. 

A bed-rock consisting of slate or schist, highly tilted, and running more or less transversely across 
the course of the stream, forms a succession of ripple-like ledges and troughs that are nearly always safe 
receptacles for alluvial gold in the conditions that commonly prevail in gold-bearing regions. 

\^^lere the bed-rock, or bottom, consists of alternating layers of slate and sandstone, the former 
will invariably arrest more gold than the latter, which, from its greater hardness and massive bedding, 
is commonly worn into smooth midulating surfaces, or sloping platforms with outlines broken only 
by an occasional pot-hole. 

The power of a false bottom to arrest the gold in a travelUng drift will depend on the character 
of the material composing the false bottom, and on the gradient. Take a local case as a typical ex- 
ample. The quartz grits at the base of the lacustrine series form a rough mat-like surface that has 
proved, on gradients giviag velocities ranging from 4 ft. to 6 ft. per second, very effective in retaining 
gold at all the places in the Cromwell basin where these beds are crossed by the Kawarau or Clutha ; 
and in witness of this we have the phenomenal dredge returns obtained in the stretch of false bottom 
lying between the Bannockburn Bridge and Kawarau Gorge. 

The greatest movement of travelling drift takes place during times of high flood. At such times 
the scour and abrasion of the bottom is abnormal, and crevices that were able to catch and retain gold 
in normal conditions may be unable to retain the gold under the stress of greater scour. Leads of 
pay-wash formed in normal conditions would also be removed, re-sorted, and again laid down in some 
lower reach or bend of the stream. In this way worked-out groimd may again become enriched. 

Reasoning from these first principles, we should expect to find the following conditions prevailing 
in connection vnth the occurrence of gold or other hea\'y mineral subject to the concentrating action 
of water running continuously in one direction, as in a river : — 

(a.) That the coarser gold would be deposited in the upper reaches of a lead. 

(6.) That the finer gold would be deposited in the lower reaches. 

(c.) That the richest and coarsest gold would be deposited in the layers of comparatively 

coarse gravel wash. 
(d.) That the finer gold would be deposited in the finer sandy drifts. 

(e.) That the best gold should occur in the layers of wash containing black sand and pebbles 
' of magnetite or other hea\'y mineral. 

(/.) That gold foimd on a steep bottom will commonly be coarser than that found on a flat- 
lying bottom, 
(g.) That in narrow reaches and in gorges the comparatively coarse gold only will be deposited. 
{h.) That no gold wiU lodge in places where the scour is too great to allow wash to rest. 
(i.) That pot-holes do not form efiective lodgments for travelling gold. 

ij.) That on a favourable bottom gold will lodge on the down side of a bar of rock running 
across the bed of a stream. 



Alluvial Gold. 
Alluvial gold in greater or less quantity is found in all the Recent and Pleistocene detrital deposits 
existing in the district, and also in some of the Pliocene lacustrine drifts. 



PT.ATE VT. 




Mouth of Shephehd's Creek, Bannockbuhjj, showing Tilted Ends of Lacustrine Series. 



Bvdletin No. 5.] 



[fo face p. Ifl. 



41 

There are seven distinct and easily recognisable classes of alluvial deposit that have been, or may 
in time become, a source of gold. They are stated hereunder in accordance with their age, beginning 
with the most recent at the top and reading downwards — that is, the deposits are arranged in the 
order of their succession in time, as shown by their superposition. 

Kecent — 

1. Crumbling schist and schistose wash. 

2. Gravels and sands in the bed of Clutha and Kawarau Rivers. 
Pleistocene — 

3. Re-sorted fluvio-glacial drift, mainly derived from 4. 

4. Fluvio-glacial deposits and moraines. 

5. FluviatUe drifts forming terraces. 
Pliocene — 

6. Sandstone gravels — " Maori bottom." 

7. Quartz drifts — " Granite wash." 

7. Quartz Drifts. — These occur at or near the base of the lacustrine series, and hence they follow 
the outcrop of that seric s around the margin of the old Cromwell basin. They form very few natural 
outcrops, being in most places buried underneath heavy detiital deposits of Pleistocene or later date. 
They crop out on the banks of the Kawarau and lower Bannockburn, but elsewhere their presence 
has only been disclosed by the sluicing-away of the overlying gravels in the course of alluvial 
mining. 

The quartz drifts are mainly composed of angular pieces of quartz of all sizes up to an inch in 
diameter. They are commonly loose and incoherent, often sandy, and sometimes clayey. 

At the mouth of Smith's Gully — that is, at the point where Smith's Creek enters the schist country 
at the foot of Carrick Range, and on the road leading from the Kawarau Bridge to Bannockburn — the 
quartzose drift is occasionally cemented by iron-peroxide into rusty-coloured layers of conglomerate. 
These layers are not continuous, and seldom over 6 in. thick. 

These drifts are important from the fact that similar drifts occurring in the same geological horizon 
have proved a prolific source of gold at Tinkers and at St. Bathan's, in the Manuherikia basin. They 
always contain a little gold ; but payable gold has only been found at the points where streams 
draining gold-bearing country have entered the old lake-basin. Keeping this in mind we should expect 
to find a payable lead in the quartz drifts somewhere near the mouth of Smith's Gully, this expectation 
being based on the knowledge that this gully has been excavated in country that is traversed by many 
veins of gold-bearing quartz. 

The lead should be looked for not at the point where the stream now issues into the old basin, 
but on the down-stream side — that is. towards Pipeclay Gully. 

The gold in the quartz drifts at Tinkers and at St. Bathan's is very fine ; and tests of the wash 
made with the prospecting-dish are not always satisfactory, notwithstanding that mining on a large 
scale has been attended with profitable results for a number of years. 

A sample of the rusty-coloured cemented drift from the mouth of Smith's Gully showed no gold 
by the dish test, but when subjected to fire assay gave a return of 15 grains of gold to the ton. 

A few colours of fine gold were obtained in the quartz drifts, by panning, at several places near 
the Chinese camp at Cromwell and between that place and Buuiockbum. 

The problem that confronts the prospector is this : Were the gold-bearing veins on the Carrick 
Range subject to denudation at the time the quartz drifts were being deposited ? The drifts, we know, 
are composed of quartz derived from the adjoining country, and the angular character of the quartz 
shows that it has not travelled far. Further, the writer has proved that fine gold at least occurs in 
the drifts. The answer in the affirmative, based on the facts disclosed here and at St. Bathan's, seems 
to be a fair and reasonable conclusion. 

The conditions for the occurrence of payable gold at Bannockburn are as favourable as at St. 
Bathan's, and for this reason the writer is of the opinion that the systematic prospecting of the drifts 



42 

should be undertaken by experienced men, special attention being given to the quartzose deposits at 
or near the base of the series at Smith's Gully and at the mouth of Shepherd's Creek, where the 
strata are inclined at high angles. 

The overlying schistose gravels at Bannockburn were very rich, the gold they contained having 
been shed by the veins on the Carrick Range after the deposition of the lacustrine beds, on the edges of 
which they lie. 

They are standing on end along the foot of Carrick Range, and at one time stood some hundreds 
of feet higher. The streams that drain the flanks of the range have cut their course across the upturned 
beds. It is obvious that any gold contained in the quartz drifts would have been concentrated to some 
extent in the process of denudation before being dropped in the schistose wash that now forms the 
high terraces at Bannockburn. 

We have no positive evidence in support of it ; but it does not seem an improbable supposition 
that a portion of the gold contained in the Bannockburn terraces was derived from a rewash of the 
quartz drifts. 

In this view, therefore, it is supposed that the quartz drifts obtained their gold at first hand from 
material shed from the gold-bearing veins, and that the terrace gravels derived their gold partly at first 
hand from the denudation of the veins, and partly from the rewash of the quartz drifts. 

6. Sandstone Gravels. — These consist of yellowish-brown sandstone gravels, well rounded, and 
fairly uniform in size. The material seldom exceeds 6 in. in diameter, and is generally much 
decomposed. 

These gravels form the well-known " Maori bottom " of the Maniototo and Manuherikia basins. 
They contain gold, but not in payable quantity. Their chief importance hes in the circumstance that 
they form the false bottom on which the younger gold-bearing drifts rest on the high terraces between 
Lowburn and the head of Five-mile Creek, and at Quartz Reef Point. 

The foreign character of the bulk of the material composing these gravels has already been referred 
to in Chapters II and III. 

At Naseby the " Maori bottom " is being worked for gold, but it has not proved very rich. 

5. Fluviatile Drifts forming Terraces. — These form the terrace known as Cromwell Flat. They 
are well seen along the banks of the Kawarau and Clutha, where they underlie the coarse, modified, 
glacier drift. 

The material composing this terrace is purely river-drift, and consists of varying proportions of 
sand and gravel. It is laid down in more or less distinct layers of varying degrees of texture. The 
coarser layers commonly contain the best gold. 

A considerable area of this drift has been sluiced away above the Chinese camp, and at the present 
time it is being cut away by a dredge at the river-edge between Cromwell and Deadman's Point, and 
is yielding payable returns. 

On the Bannockburn side of the Kawarau, opposite Cromwell, and between Cromwell and Dead- 
man's Point, this drift rests on the schist bottom — that is, it lies on the schist around the margin of the 
old lake-basin. Towards the dip it passes off the schist or " reef " bottom on to the lignite series, which 
dips away to the westward. 

The outcrop of the upper members of the lignitic series, as seen in the upper end of the deep tail- 
race half a mile above the Chinese camp, shelves rapidly under water-level into what appears to have 
been an old channel of the Kawarau, running parallel with the present face of the terrace at this 
place. 

A quarter of a mile above the tail-race the Kawarau issues from a channel cut in the schist ; and 
at the Bannockburn Bridge the river runs through a similar rock-cut channel. 

These rock channels are of comparatively recent date, and are merely short cuts that the river has 
made for itself through flat spurs of schist that projected into the old basin. 

Coming back to Cromwell we find that a knob of schist, removed in 1906, stood above the level 
of the terrace near the Domain. The writer was fortunately able to examine this knob before its re- 
moval. By many it was erroneously spoken of as a boulder, but its large area and the conformity of 
the foliation to that of the schist on the river-side showed that it was in situ. 



43 

In these facts we have conclusive evidence of the existence of an old channel of the Kawarau 
that started some 12 chains above the Bannockburn Bridge and passed down towards the back 
of Cromwell, keeping outside the flat schist spurs through which the present channel of the Kawarau 
is cut, and reaching as far as the Roman CathoUc church, near which it joined an old channel of the 
Clutha. 

The united channel seems to have skirted the schist knob near the Domain, perhaps reaching 
as far as the present bed of the Clutha whence it swept somewhat abruptly to the south, keeping outside 
the area of schist through which the Clutha now runs immediately above Cromwell Bridge. 

That a lead of gold passes through this old channel is not quite certain, but is highly probable. 
But to work this deep lead, assuming that it does exist, is quite impracticable without destroying a 
large portion of the Town of Cromwell. 

The dredge now at work in the Clutha a mile above the Cromwell Bridge, is nibbling at the edge 
of the bank somewhere near the course of the old channel, and if the ground is not too deep it may 
be able to demonstrate the existence Of a deep lead running under the terrace towards the Roman 
Catholic church. 

The edge of this old channel might also be reached by a powerful hydraulic elevator plant 
at the top end of the old tail-race above the Chinese camp ; but the overburden is everywhere 
very deep. 

Leads at Quartz Reef Point. — There are three alluvial leads at this place, known as No. 1 or River 
lead, No. 2 lead, and No. 3 lead. These leads run more or less parallel with the present course of the 
Clutha River, and are old gutters formed by the river at different levels as it cut its way down to its 
present charmel. They were very rich, and, although no longer being worked, are of great interest 
irom the light they throw on the distribution of the gold along the old channels of the Clutha. 

For the following information, which is supplemented by personal observation, the writer is in- 
debted to Mr. William Tillman, an experienced miner, who has worked in this locality for twenty 
years. 

No. 1 or River lead runs along the present bank of the river, the pay-wash lying some 8 ft. or 10 ft. 
below the normal water-level. It follows an old channel excavated in the schist. The best gold was 
obtained against the western or river-side rim of the channel, which is about 100 ft. wide. 

No. 2 lead lies from 3 to 4 chains east of No. 1, and is some 15 ft. higher. It is confined within 
rims of schist, and its width varies from 1 to 3 chains. 

No. 3 lead is some 10 chains still further east, and lies at a higher elevation than No. 2 lead. It 
is some 12 ft. or 14 ft. below the level of Quartz Reef Creek, under which it runs. Its width at the 
bottom was about 40 ft. 

The pay-wash on the south side of Quartz Reef Creek, and for some 5 chains north of that creek, 
rested on a schist bottom, but going northward it passed on to a clay bottom which is a part of the 
lacustrine series. It was found to be richer on the true than on the false bottom. 

No. 3 lead was driven on, going south from Quartz Reef Creek, for a distance of 120 ft., when it was 
cut out by a heavy schistose drift lying in an old channel coming from the oast that cut across it at 
nearly right angles. The wash is said to have been highly payable up to the point where it was cut off. 

The material filling the old channel consisted mainly of creek-wash mixed with numerous large 
semi-angular masses of mica -schist, through which it was practically impossible to drive. 

With the view of picking up the lost lead on the far side of the intersecting gutter, a low-level 
drive was put in for a length of 800 ft. from a point some distance lower down Quartz Reef Creek ; but 
the ground proved very heavy, and the drive collapsed before the desired point was reached. 

Nos. 2 and 3 leads were worked mostly by sinking shafts and then driving out the wash, and both 
proved highly payable. All of the leads were cut through by lateral streams, which interrupted the 
continuity of the pay-wash. 

No. 1 lead has been worked at different points for a distance of some 15 or 18 chains ; No. 2 for 
about 20 chains ; and No. 3 for 9 or 10 chains. 

South of Quartz Reef Creek Nos. 1 and 2 will be cut off by the Clutha River, which at a compara- 
tively recent date cut back at this place towards the foot of the higher terrace. 



44 

No 3 lead, on the other hand, so far as we can judge from the surface indications, ought to con- 
tinue far down the valley, the terrace under which it passes being unbroken for a distance of 30 chains. 
The prospecting of this lead is a work that seems to hold out a fair promise of success. 



N^3 LeoLcL 



ir>2Leadi 



CluthcL. River 
N^lZecLcL 




Fig. 14. Section showing Position of Gold Leads at Quartz Reef Point. 
Scale, 5 chains to an inch. 



4. Fluvio-glacial Deposits and Moraines. — Every glacier that descends a valley is drained by a 
river ; hence, country that was once overrun by a glacier is found to contain two classes of transported 
material — namely, one transported by ice, the other by water. 

The glacier carries on its back a load of broken rock and rocky debris that have fallen dowrt from 
the high lands on each side of the valley. Hence we find that the load is not spread evenly over the sur- 
face of the ice, but occurs as long lines, one on each side of the glacier, as sho'wn in the next figure. 




Fig. 15. Section of Glaciee above Terminal Face. 
o. Moraines. b. Basement rock. c. Glacier tunnel. d. Glacier ice. 



As the ice advances the rocky load is carried forward, and in time reaches the end or terminal 
face of the glacier, where it is tipped and piled up in a confused mass on each side of the valley. 

The river which drains the glacier brings down the usual gravels and sands found in river- 
beds. 

At certain points below the terminal face of the glacier the morainic matter and river-gravels 
are mingled in the manner shown in the following figure : — 




Fig. 16. Section of Glacier Valley below Terminal Face. 
a. Glacier moraines. b. Glacier river-gravels. c. Basement rock. d. Glacier river. 



Where the country is gold-bearing, the glacier gravels and morainic matter contain gold. But 
the moraines are formed by ice, which cannot sort the gold from the rocky debris ; hence the gold 
is scattered through the debris just as the glacier happened to drop it. 



PLATE VII. 




MoilII OK KawaHAU GoHGE, TAKliX FHOM SUMMIT OK MOKAI.Nl!; 




Uulletin No. J.] 



MOLTH OK KaWAUAC GoiiGK, C'HOirWEI.I, 



\_Tu face. p. Jflf. 



PLATE VIII. 




KaWAUAU MulfAI.NK, Cl!OM\Vi:i,L 




Bulletin Xo. 6.] 



ICE-SIIOiJX liOCK XICAli KAWAliAU BuiDGE, GlIUiSTON. 



[To face p. .'/.'f. 



45 

Even at the places where the morainic matter and the gravels mingle the gold is not 
concentrated into leads, but occurs in pockets, where the current has been arrested by large ice-borne 
rocks. 

A glacier deposits morainic and fluvio-morainic matter both in advancing and retreating. But 
the matter deposited during the advance is broken up and overrun by the ice, while that dropped during 
the retreat remains in the wake of the glacier. 

Morainic matter left in a valley is often re-sorted by the glacier river, and in this re-sorting process 
any gold present in the drift becomes more or less concentrated into leads. 

The fluvio-glacial deposits at the lower end of the Kawarau Gorge are typical examples of the class 
of glacier transport-work described above. 

The Kawarau moraine, three miles from Cromwell, is composed of rocky matter that fell from the 
Pisa Range side of the gorge on to the advancing ice. It is therefore a lateral moraine. 

On the lower face it is mixed •with gold-bearing river-wash ; and several paddocks have been taken 
out in it a few chains back from the main road, but on account of the difficulty and danger of working 
among large morainic boulders the operations were conducted on a small scale, and in every case confined 
to the talus slope of the moraine. 

3. Re-sorted Fluvio-glacial Drift. — The gravels formed by the glacier river are largely a rewash 
of the morainic matter tipped into the valley at the terminal face of the glacier. 

When the glacier begins its last retreat, the river, having little supply of fresh matter to operate 
on, devotes its energy to cutting away and destroying the lateral moraines that were formed along the 
old line of retreat. 

The existence of Clyde moraine, and the presence of the fluvio-morainic matter which we find 
spread over the lower end of Manuherilda basin, tell us that the Clutha-Kawarau glacier occupied the 
Dunstan Gorge for a considerable period. At one time this great glacier reached as far as Alexandra, 
where it blocked the outlet \\-ith debris to such a height as to permit the accumulation of the fluviatile 
and fluvio-glacial drifts that form the terraces between Springvale and Clyde. 

The glacier retreated from Clyde and took up its next stand at Cromwell, where the outlet in time 
became blocked by the piled-up morainic matter. Then began the accunmlation of the fluvio- 
glacial drifts composing the flood-plain, of which the high terraces that fringe the Cromwell basin are 
a remnant. 

After the filling-in of the debris-blocked basin, the outlet began to be cleared out, and then com- 
menced a period of destruction, during which the flood-plain was benched into the terraces we now see 
in the basin. 

During this period of fluviatile destruction the Kawarau glacier entrenched itself in the Kawarau 
Gorge, where, sheltered by Pisa Range from the northern sun, it piled up a moraine along its exposed 
face. 

The Clutha glacier beat a retreat at the same time, and from the small amount of morainic matter 
left behind we can conclude that its recession was relatively rapid and continuous. For unlike the 
Kawarau glacier, which lay snugly sheltered in a deep gorge, it occupied a wide open valley exposed 
to the blaze of the morning and noonday sun. Hence it tarried nowhere, but receded rapidly to the 
upper end of the valley without leaving any morainic piles to mark its line of retreat. 

After the reopening of the outlet, which, as we have seen, was accompanied by the excavation and 
benching of the flood-plain not long formed, the Kawarau glac'ier once more advanced to Cromwell. 
Its narrow front ploughed out a chamiel in the fluN-iatile drifts forming Cromwell Flat. 

The glacier soon began its final retreat, scattering in its wake a confused mass of river-drift and 
morainic matter, which follows pretty closely the present course of the river. 

This fluvio-glacial matter, since partially re-sorted by the river, was the source of the bulk of the 
allu\nal gold found in the Cromwell district in the " seventies." It occurs on both sides of the 
Kawarau near Cromwell, and has long since been turned over. 

It also forms the tongue of land on which the lower part of Cromwell is built, and thence passes 
up the west bank of the Clutha to Deadman's Point. The drift in this last stretch is probably the 
trail of the Clutha glacier. 



46 

This re-sorted glacier drift rests on a denuded surface or false bottom of the purely fluviatile drifts 
that form Cromwell Flat. Its distribution, and the portions that have been removed by sluicing along 
the river-face, are shown on the special map of Cromwell facing this page. 




Fig. 17. Section across Kawarau River near Cromwell. 
a. Mica-schist. h. Fluviatile drifts. c. Re-sorted fiuvio-glacial drift. 



Perhaps the only extensive area of this rich drift that now remains intact is that which lies imder 
the Township of Cromwell, in the narrow tongue of land lying at the junction of the Clutha and 
Kawarau Rivers. To work this ground effectively would mean the destruction of the lower end of the 
town ; and as the results would hardly justify this course, it is obvious that much wealth must lie 
buried here for all time. 

2. River-bed Gravels and Sands. — These occupy the beds of the Clutha and Kawarau Rivers. They 
vary in depth from 2 ft. or 3 ft. to 20 ft., according to the velocity of the current and the depth of the 
channel. 

Throughout the Dunstan and Kawarau Gorges these gravels, commonly spoken of as river-wash, 
rest on the schist bottom. From Cromwell to Deadman's Point they also rest on the schist, but beyond 
the latter they pass on to the lower members of the lignitic measures. 

From the Chinese camp to the first rocky gorge, a mile or more from Cromwell, and from the upper 
end of this gorge to the mouth of the Bannockburn, and again from a point a few chains above the 
Bannockburn Bridge to the Kawarau Gorge the Kawarau river-bed wash rests on the different members 
of the lignitic series. 

The only practicable method of winning the gold lying at the bottom of this river- wash is dredg- 
ing. Dredges have already turned over the greater part of the Kawarau River bed from Cromwell 
to the Kawarau Gorge, and the experience gained during the course of the operations showed that the 
richest gold occurred where the river-wash rested on the quartz drifts. These quartz drifts occur, as 
we have seen, in two horizons — namely, at or near the base of the lignitic series, and at the top of the 
series as exposed at Bannockburn. 

1. Crumbling Schist Wash. — The most notable examples of this class of wash are to be found on 
the flanks of the Carrick Range above Bannockburn. The schist wash along the bottom of Adams's, 
Smith's, and Pipeclay Gullies and their numerous branches has been carefully turned over in the search 
for the precious metal. Even the crumbling schist that has accumulated in shallow hollows and dry 
gullies has often proved highly payable. 

This class of dirt nearly always contains a good deal of gold adhering to pieces of vein-quartz. 
Moreover, the bulk of the gold is honeycombed, and bears evidence of having been shed by gold-bearing 
quartz veins in the vicinity. Such is the case near Bannockburn. There we find that the creek-wash 
is gold-bearing only where a gold-bearing vein occurs within the drainage-area of the creek. 

It is obvious that gold-bearing wash of this kind must be limited in extent, being necessarily con- 
fined to areas in which the outcrops of quartz veins have been subject to denudation. It should also 
he noted that the outcrop of the vein which shed the gold is not always exposed at the surface. In 
some cases schist wash carrying good gold has. been traced almost up to the crest of the dividing ridge. 
In such cases a search should be made for the vein by trenching across the spurs. 



Tb accompcoiy JBzdletiTi ]V° S, CrojnwelX SuhdivisiMnWesterrv Otuqo Division. 

Geological Map of 

OF CBIOIMJWELL TOWNJSHIJP 

Showing distribution of Fluvio -Glacial Drifts 
at Junction of Clutha and Kawarau Rivers. 




Reference to Geological colours 



PLEISTOCENE. 




PLIOCENE PALEOZOIC 

Manuharikia Series ManioToto Series 



n n □ □ 



ZowefScfiises Oid'i^rkings 



Scale of Chains 



(geology 'by Jbcmes Park . 
TopographicaZ data, Tnatnly sup- 
■plied try the Lands and. Survey 
Dept. and. partfy irom- oHglTtaV 
survey hy A-Q-MacdoyxaZd- under 
Jaraea Faj^ direction' 



JAtAZ^ MACKINTOSH BELL 



bJ^J^:^ 





Kawarau River 




Crorr\well 


Clutha River 

Road 


/--^ 






-U< 


-"^-J."p)'t—r:-^ 








Jj^ ^ 


== 














i.'. 


. 





J)rawnbyG.EIIarru>,SepCrJ307 



SECTION ALONG LINt A-B 



lutHBiuimMiuiunjuuuuua 



47 

Most of the known deposits of this class of wash have been worked out, but there is reason to beheve 
that new deposits may be discovered on the Dunstan Range, in the undulating tussock land lying between 
Castle Rock and Thompson's Creek ; and on the western upland flanks of Pisa Range, more especially 
in the area lying between Moonlight and Mitre Creeks. 
The chief characteristics of this class are as follow : — 
a. Ground generally shallow. 

h. Confined to the bottom of small streams and hollow places lying below the outcrop of gold- 
bearing veins. 

c. Gold commonly honeycombed. 

d. Pieces of gold-bearing quartz are often found in the claims lying near the source of the gold. 

The Blowing-down System of Sluicing. 

This is a novel system of sluicing that has been successfully used for the working of wide stretches 
of poor alluvial ground in Central Otago. Its greatest application has been in the Cromwell district, 
where it has been in use for over thirty years. It was first introduced by a Russian miner, and, 
although so long in use, is almost unknown outside of Central Otago. 

(Scope 0/ System. — This system can only be applied to the working of alluvial ground (a) where 
the wash lies on a sloping bottom, having a gradient of not less than 1 in 3 ; {b) where the wash is 
shallow — that is to say, not exceeding 6 ft. ; and (c) where large stones are absent — that is, the stones 
should not be too large for two men to handle. 

The Actual Working. — In ordinary sluicing, whether ground-sluicing or hydraulicing, the practice 
is to begin operations at the lowest part of the ground, and to work forward on the rising bottom, the 
main tail-race being extended as the working-face recedes. This is working away from home. 

In the blowing-down system the main tail-race is carried to the boundary of the ground before 
the sluicing is started. After the tail-race is constructed a side race or gutter of smaller dimensions 
is carried along the boundary. Two strips of ground about 3 yards wide, one on each side, are now 
sluiced into the gutter, beginning at the top of the slope. This is working home. 

When the strips on each side of the gutter reach within a yard or two of the main tail-race another 
gutter is carried up the slope parallel to the first, and the sluicing operation is repeated, and so on, the 
ground being cut away in parallel slices. 

Let the following figure represent the plan and profile of a piece of alluvial ground, and let the 
natural drainage of the land be in the direction shown by the arrow : — 



If 




Flu. 18. Showing Plan .and Profile of Gravel Wash besting on Sloping (iaouND. 



In the above figure, a is the main tail-race, b the side gutter, and c the cross-trench where the 
sluicing begins. 

The trench c is cut out the full width of the paddock or strip to be washed down. It need not be 
cut down the full depth of the wash, as the water soon excavates it down to the bottom. It is merely 
the starting-point of the operations. 



48 

The stones are thrown back and stacked on the sluiced ground as the work proceeds. 

The water is brought on to the top part of the ground in pipes, which are extended from time to 
time as the ground is cut away. It is conveyed from the pipe-Une to the working-face in a stout canvas 
pipe 7 in. in diameter, and provided with a nozzle at the end. The nozzle is held in the hand or rests 
on a movable tripod. 

The canvas pipe is made in convenient lengths of 18 ft. or 20 ft. As the face recedes fresh lengths 
are put on, being simply telescoped into each other for two or three feet. The joint thus made becomes 
quite tight when the water is turned on. 

In some cases two paddocks are washed down at the same time, and it is claimed that this system 
effects a considerable saving of time, as when one gutter becomes choked ■v\'ith stones sluicing can be 
carried on in the other. The work thus goes on continuously in one paddock or the other. 

In this system of working there is practically no shovelling or forking, the only manual labour 
involved being the stacking of the stones. 

Alluvial miners claim that when the jet of water is directed downhill the cleaning-up of the bottom 
is much more efEective than when it is directed upward, as it is in ordinary hydxaulicing. In the 
latter case the tendency of the jet is to drive the particles of gold into crevices, where they cannot be 
dislodged wathout breaking up the bottom. 

The canvas used is 24 in. wide, sold in bolts containing about 42 yards. With a lap of IJ in., 
this width gives a hose about 7 in. in diameter. 

Messrs. J. Swan and J. Werner, two experienced miners, without assistance sluiced away 10 acres 
of wash in two years. This is equal to 2| acres per man a year. The depth of the wash varied from 
ft. to 5 ft., the average being about 2 ft. 6 in. 

The blowing-down system is admirably adapted for the working of poor shallow ground that 
happens to rest on a bottom having the requisite slope to enable the water to carry the dirt down the 
side gutters into the main tail-race, where the gold is caught. 

It should be mentioned that it is sometimes found to be advantageous to allow a supplementary 
supply of water to run down the main tail-race, in order to keep it clear of debris. Further, the greater 
the pressure of water at the nozzle the quicker will the ground be sluiced away. 




Fig. 19. Showing Blowing-down Systjcw of Slcicino. 



Gold-bearing Lodes. 

There are two great systems of lodes in this district, one at Bendigo, the other at Carrick Range. 
Both occur in the schists of the Maniototian, the Bendigo veins in the lower part, and the Carrick 
veins in the higher. 

The Carrick system consists of a number of small lodes running within more or less well-defined 
walls. The lode-matter is chiefly crushed rock, which commonly encloses one or more ramifying veins 
of quartz. None of the old workings appear to have reached below the zone of oxidation. 



PLATE IX. 




Low HuiiN Vai.i.ey, NEAii SouiiCE, SHOWING PiSA 1{am;i-; IX Uackgkound. 




.Showing ■' Blowing-down ' Sy:^tem ok Working Alluvial Guolnd, Lowulkn, Centhal Otai;o. 
UuUctin Xo. .5.] iTo face p. .',>i. 



Pr,ATE X. 




LowBURN Terraces, lUioii Deadman's Point, Cuomwkll. 



Bulletin No. 5.] 



(To face p. j^. 



49 

The Bendigo lodes are somewhat similar in character, but were found to carry good values into 
the blue unoxidized ground. 

Along the course of the upper part of Rise and Shine Creek there is a shear-zone, along which a 
certain amoimt of mineralisation has taken place. This also occurs in the lower schists, which are 
nearly horizontal. 

A singular feature in connection with the geology of the Bendigo and Carrick Goldfields is the 
absence of all trace of igneous intrusions. 

Although vein-mining has now ceased at these places, a close examination was made of the lodes 
with the view of finding out the characteristics peculiar to the place, and of collecting data for general- 
isations that might be applied with profit to other parts of the district, 

BENDIGO GOLDFIELD. 

Situation. — This goldfield is situated on the slopes of the Dunstan Range facing the Clutha Valley, 
at a point about four miles below the junction of the Lindis. 

The old Bendigo Mine and battery are situated at an altitude of some 2,000 ft. above the sea, or 
about 1,000 ft. above the Clutha terraces. 

Access. — The goldfield is about thirteen miles from Cromwell, and is reached by a good cart-road 
which follows the east side of the Clutha for the first ten miles. The next mile or .so is across the 
terraces, beyond which the road rises by a steep gradient for the remainder of the distance. 

Discovery. — The Bendigo Mine was first opened out in 1865 by Logan and party, who worked 
there until 1876, when the Cromwell Company was formed. It was at this time said to be one of the 
best gold-producers in the colony, and some of the shareholders were reported to have received in 
dividends amounts varying from £50,000 to £80,000.* Altogether, Logan and party are stated to have 
obtained gold to the value of £500,000. (" Handbook of New Zealand Mines." 1887.) 

Between 1876 and 1883 the Cromwell Company obtained 26,000 oz. of gold. Between 1894 and 
1899 some 2,400 oz. of gold were raised, mostly by tributers. In 1900 the mine was closed down, and 
is still idle.f 

Rocks. — The country rock is a hard, highly altered and contorted quartzose mica-schist, in places 
passing into a micaceous quartz-schist. It occurs well down in the succession of schists forming the 
Maniototo Series. 

Vein-systems. — The Bendigo mining-area is traversed by two distinct vein-systems — namely, one 
running about N.E.-S.W., and the other running approximately E.-W. The veins of the latter system 
have proved the more permanent and productive. The veins of the former system are locally termed 
" cross-lodes." 

Cross-lodes. 

The Cross-lode. — This lode intersects the east-and-west lodes near the site of the old battery. It 
strikes N.E.-S.W., and dips towards the N.W. at an angle of about 70". 

As seen in the* trenches along the line of outcrop its wndth varies from 2 ft. to 4 ft. The walls are 
well defined, more especially the foot-wall, and, although sharply outlined, do not exhibit any signs 
of wall-movement. 

The vein peters out going in a south-west direction, the quartz on the edge of the road about 4 cliains 
from the old battery having dwindled down to nothing. 

The track of the vein-fracture can be traced across the road for a distance of .3 chains, but beyond 
that it disappears altogether. 

At the point where this cross- vein runs out it is joined on the foot -wall side by a small vein of 
quartz, which runs in an east-north-east course, thus striking directly for the old stone smithy. This 
small foot-wall vein varies from 6 in. to 12 in. wide. Except a small shallow trench about 8 ft. long, no 
work appears to have been done on it. 



* "New Zealand Mining Handbook," lOOG, )«. 375. 

t The history and development of the mine is given by >Tr. Robert Mcintosh, A.O.S.M., in an intereatfug article 
in the " New Zealand Mining Handbook," 1900, p|>. 158-60. 

4 — Cromwell. 



50 

Going in a north-west direction the cross-lode intersects successively the South lode, the Cromwell 
lode, Middle lode, and North lode. The line of outcrop passes under the battery-house, but there is no 
surface indication of it beyond that point. 

East-and-west Lodes. 

North Lode. — This lode runs 5° south of east — that is, nearly due east and west. Its course is 
indicated on the surface by open trenches and shallow pits for a distance of several chains. So far 
as could be known from an examination of the old workmgs, it appears to have varied in width from 
1 ft. to 3 ft. 

The walls are fairly distinct, and are vertical or inclined towards the south at an angle of 
about 80°. 

In a shallow trench and small shaft 3J chains north-east of the old battery, the North lode is seen 
to consist of two well-defined walls varying from 2 ft. to 3 ft. apart, and enclosing a rib of compact 
quartz a few inches thick on the foot-wall. The remainder of the lode-matter is mica-schist, much 
weathered and more or less crushed. 



!• 3 




Fig. 20. Cross-section of Nokth Lode, Bendigo. 
a. Cnished mica-schist. 6. Quartz vein. c. IVIica-schist. 

Cromwell Lode. — This has proved the most important gold-bearing lode at Bendigo. It is stated 
to have yielded the bulk of the gold obtained on this goldiield. 

Its width, as seen in the extensive underhand stopes which follow its outcrop, A^aries from 1 ft. 
to 5 ft. • 

The course of the lode is 20° south of east. The walls are vertical or shghtly iucUned towards the 
north, and generally sharply defined, more especially the foot- wall, which passes in and out in a sinuous 
course. 

The lode-matter consists mainly of crushed and decomposed mica-schist, through which there are 
a few ramifying veins of quartz, mostly on or near the walls. In many places the lode widens out 
in going down, as shown in the next figure. 





Fig. 21. Ceoss-section and Enlaeged Sectiox of C'komwell Lode at 3 Chains west of Batteey. 
a. Quartz veins in lode-stuff. b. Mica-schist. c. Crushed schist. 



The Cromwell lode going westward towards the Clutha can be traced by surface outcrops for some 
15 chains west of Battery Creek, under which it passes, until it disappears below the high-level Pleisto- 
cene terrace gravels at an altitude of about 1,400 ft. above the sea, 



PLATK XI. 




JJemju.o Mi.m., m:.vi; Ci(OMu 1,1.1,, L'l.uiii.v \'.\i.i.i;y. 



Bulletin No. 5.] 



I'J'o face J). .'lO. 



51 

A prospecting shaft, sunk in the terrace 10 chains from the boundary of the schist and on the course 
of the lode as projected from the outcrops further east, reached a depth of 60 ft. mthout finding the 
bottom of the gravels. 

In the trenches along the outcrop, on the high ground lying between the terrace and Battery 
Creek, the lode varies in width from 1 ft. to 3 ft. The lode-matter, as elsewhere, is mainly crushed 
mica-schist intersected by quartz veinlets, but in a few places the quartz is 3 ft. wide ; but this width 
is not maintained for any great distance. 

The quartz is generally grey or reddish brown in colour. It is crystalUne in structure, is often 
faintly banded, and in places possesses a comb -structure in the middle of the vein. 

The lode does not appear to have been worked on the west side of Battery Creek, although some 
shafts and trenches would indicate that it has been prospected with some care in that direction. 

The character of the lode is well seen in some of the prospecting shafts on this side. 




Fig. 22. Cboss-section of Iromwell Lode in Third Pro.spectinc Shaft, 3 Chains from Terrace. 
a. Quartz vein. h. Crushed schist. c. Mica-schist. d. Foot-wall vein. 



The same lode is exposed in a prospetting shaft on the top of the hill, over against the battery, 
at a point some 10 chains from the terrace. Here the quartz vein has moved from the foot-wall to 
the middle of the lode. 




Fif;. 23. Cross-section of Cromwell Lode in PRosrEi-TiNG Shaft on Hill west of Battery Creek. 

a. Quartz vein. 6. C; ushed schist. c. Mica-schist. 
4* — Cromwell. 



52 

The rapid way in which the ramifying veins in the lode change in shape and direction, even in the 
space of a few feet, is well seen in an old prospecting shaft on the edge of the hill overlooking Battery 
Creek. This shaft is sunk on the line of lode, and is 4 ft. 3 in. by 5 ft. 

At the east end of the shaft the section of the main vein of quartz is something hke that shown 
in the last two figures, but at the west end, only 5 ft. away, new veins have appeared, and those seen 
at the other end are so different in size and arrangement as to make it difiB.cult to correlate them with 
those at the east end. 

The next figure shows the veins as they appear in the lode at each end of the shaft. 




Fig. 24. Plan and Cross-sections of Cbomwell Lode in Prospecting Shaft. 
a. Quartz veins. h. Lode-matter consisting mainly of crushed schist. c. llica-schist. 

The section at A B was taken looking east. The section at C D was taken looking west, but was 
reversed in drawing so as to be seen as if taken looking east, for the purpose of comparing it vdih the 
section at A B. 

The Cromwell lode, from the old battery going eastward, has been worked by an open trench 
varying from 5 ft. to 9 ft. wide. Below the open cut the lode has been beaten out to an unknoMoi depth 
by an underhand stope, which is very narrow, having been carried down only on the main body of quartz. 
In the open cut the lode has been broken out from wall to wall, the daylight character of the work 
doubtless having enabled the ore in the small quartz veinlets to be sorted out of the mullock at small 
expense. 

A little to the south- we.st of No. 1 shaft a small cross-lode, varying from 12 in. to 24 in. wide, runs 
from the Middle lode to the Cromwell lode, this last being intersected at an acute angle. 

This cross-lode passes through the Cromwell lode, which is only slightly displaced, and pursues 
a course towards the pumping-shaft. It has been worked out for some depth by a surface stope. 




Fig. 25. Plan showing Inteesection of Cromwell and Cross Lodes. 
aa. Cromwell lode. bb. Cross-lode. 



53 

The Cromwell lode throws out two small branch lodes from its south wall. These leave the branch 
lode at an acute angle, the one near No. 1 shaft, the other near No. 2 shaft. 

Both branching lodes are nearly vertical, and have clearly defined walls. They var\' from a few 
inches to 2 ft. wide. They have been worked out for some depth and distance along the strike by 
underhand stopes that began at the surface. The lode-matter in them consists mainly of crushed 
mica-schist, through which run small veinlets of quartz that open out in places into large blocks 
of compact stone. 

The South Lode. — This lode Hes immediately south of the Cromwell lode, with which it runs parallel 
imtil a point is reached about 2 chains east of the old stone clock-house, where it bends rather abruptly 
to the south, now following a course about 12° south of west. 

At its west end it is opened up by a drive, which follows the strike for a distance of some 70 ft. In 
the roof of the drive the lode is seen to possess a well-defined foot-wall, which dips to the south at an 
angle of 75°. The hanging-wall is not easily distinguished, as the schist on this sit'e is intersected by 
several joint-planes running parallel with the foot-wall. 

The lode-stufE consists of a thin layer of broken quartz and clay lying on the foot- wall. Above 
this lie several inches of rotten schist, traversed by a thin vein of quartz. 



I 

^ I 

1 



_1 

N 




-b c 



Fid. 26. ("ross-section of South Lode. 
a. Quartz vein and clay. b. Joint.s. c. ilica-.schist. 



The Bee Lode. — This lies to the south of the South lode, its course being about east and west, or 
nearly parallel with the Cromwell lode. 

It crops out on the spur opposite the prospecting drive on the South lode. Here it has been exposed 
in a shallow pit and in a trench a few yards long. 

The walls appear to be well defined, and about 2 ft. apart. 

The ore-body consists of crushed and decomposed mica-schist, through which there run small 
veinlets of rusty-coloured quartz. 

So far very little prospecting has been done on this lode. The contour of the ground is, however, 
eminently favourable for the construction of a drive along the course of the lode, giving a height of 
40 ft. of backs on the west end and 175 ft. on the east end. 

Hit or Miss Lode. — About 7 chains further south and a hundred feet higher up, a lode, believed 
to be the Hit or Miss lode, crops out on the Bee .'^pur. It is similar in character to the lodes already 
described. It has been opened up by a number of shallow troiulio-; find a few shallow shafts placed at 
intervals along the outcrop. 

The lode is vertical, and appears to vary from 6 in. to .3 ft. wide, as seen in the side of the deepest 
shaft. The strike is 110° (true). 

Aurora Lode. — This lode and the next four crop out on the crown of a ridge that runs down to 
Bendigo Creek. It is situated about a mile east of the pumping-shaft on the Cromwell lode. 

It has been opened up by a long trench, three shafts, and an underhand stope. Its course, as 
indicated by the line of trench, is about 115° (true). It is vertical, or slightly inclined to the south- 
ward. 



54 

The walls are well defined. On the crown of the spur on which the main workings are situated 
the ore-body is found to vary from 2 ft. to 6 ft. wide, and to consist of rotten schist and thin interlacing 
veins of quartz. It can be traced along the surface for a distance of 5 chains, the outcrop having been 
located at different points by shallow pits and trenches. 

Anderson^ s Lode. — This is parallel to the last lode, and lies about 4 chains further down the spur. 
It is well exposed in a deep narrow trench, situated a few chains to the east of the spur on which the 
main outcrops occur. 

Its course is east-west (true), and it stands practically vertical. The south wall is clearly defined. 
The north wall is somewhat indistinct. 

The lode-matter varies from 15 in. to 36 in. wide. In the face of the main trench it is seen to con- 
sist of a band of fairly solid quartz lying near the north wall, and of crushed schist on the opposite 
wall. 



i»/5» 




Fig. 27. Ceoss-section of Anderson's Lode, 
a. Quartz vein, 



h. Crushed mica-schist. 



c. Mica-schist. 



Lucknow Lode. — This lode is parallel to Anderson's, and crosses the spur about 4 chains lower down. 
Its strike is 85° (true), and the walls are vertical or incline slightly to the south. The walls follow 
a somewhat sinuous course, and are not well defined. 

The lode has been worked along the outcrop by a trench and underhand stope for a distance of 
5 chains. 

The width of the ore as seen in the open cut varies from 2 ft. to 7 ft. The lode-matter itself con- 
sists mainly of broken and crushed schist, through which run thin veinlets of quartz, some of which 
open out in places into large lenses of sohd ore. 

The lode on the crown of the spur is crossed by several cross-lodes, two of which have caused a 
small amount of displacement at the point of intersection, as sho-woi in the next figure : 




Fig. 28. Plan of Luoknow Lode, showing Displacement by Ceoss lodes. 



55 



Bradford's Lode. — This lies about 2 chains further down the spur, and runs nearly parallel with 
the last. The walls are sharply defined. The lode is well exposed in a natural cleft in the rock, 
where it shows a width of 12 in. 

No work of any kind appears to have been done on this lode, which, like the others, consists mainly 
of crushed decomposed rock, enclosing irregular strings of quartz. 

Low-level Adit. — About 20 ft. above the bed of Bendigo Creek, at a point nearly in a line with 
the spur on which the lodes last described occur, there is an old adit rumiing 170° (true). 

At 25 ft. from the mouth the adit is crossed obliquely by a muUocky lode, varying from a few inches 
up to 3 ft. wide. Its course is 135° (true). The walls are smooth and slickensided. Going eastward it 
has been driven on for a distance of 40 ft. 

Alta Lode. — This crops out at the head of a small gully just over the western spur leading down 
to Bendigo Creek. The outcrop has been proved by shafts and trenches for a distance of half a mile. 

As seen in the workings furthest east, the lode consists of a narrow zone of crushed rock running 
parallel with the lode-fracture. Further down the hill it follows an irregular siimous course, with an 
average dip of 75° to the north. 

In the shaft 2 chains from the top of the hill the hanging-wall is well defined, but the foot-wall is 
indistinct. 




N ' 

— - — f/f ' J 

CO. & o- 

Fio. 29. Cboss-section of Alta Lode. 
a. Quartz vein. h. Crushed rock. c. Mica-schist. 



Three chains below the shaft referred to above there is another shaft 60 ft. deep, in which the lode 
has dwindled down to 5 in. between the walls. A chain further down, the lode splits into three 
branches. The ore at the point of intersection has been worked out. 

At a point 2 chains fiurther on, the lode as seen in an open cut is almost vertical, and both walls are 
sharply defined. The lode-matter is here 9 in. wide, and consists of quartz, which at a depth of 2 ft. 
is split into two legs by a wedge of crushed rock, as shown in the next figure : — 




Fio. 30. Cross-section of Alta Lodk in Open Cut. 
a. Quartz vein. h. Crushed rock. c. Mica -schist. 



56 

A little below this a quartz leader crosses the lode at an acute angle. It strikes 300° (true), and is 
almost vertical. There is a slight displacement of the north wall. 

Some 6 chains lower down the lode has widened out to 6 ft., containing two strong veins of quartz, 
one of which is forked into two branches near the surface. 




Fio. 31. Cross-section of Alta Lode above Mouth of Old Drive near Battery. 
a. Quartz veins. h. Crushed rork. c. Mica-schist. 

Below the drive described above there is another drive nearer the battery, which cuts the lode 
60 ft. from the mouth. 

At 30 ft. in, this drive crosses an 18 in. mullocky leader, with well-defined slickensided walls, 
running parallel with the Alta lode. 

After reaching the Alta lode the adit follows the course of that lode for 100 yards. In this distance 
the ore-body varies in width from 2 ft. 6 in. to 6 ft., and is contained between vertical, well-defined, 
slickensided walls. It consists mainly of crushed rock and irregular veins of quartz and scheehte. 

On the north wall there lies 3 ft. of crushed and decomposed rock, and on the south wall 2 ft. of fairly 
solid promising-looking quartz. ScheeUte occurs on and near the south wall, disseminated through 
the quartz in small bunches. 

A small parallel leader, whose outcrop has been located by pits and trenches for a distance of a 
mile, lies about 3 chains still further south. Between this leader and the adit there is a second parallel 
leader opened up just above the battery. Thus we have three leaders on the south side of Alta lode. 

About half 'a chain to the north of the main lode there is another parallel leader, and still another 
over the spur facing Bendigo Creek, just above the old battery-site. 

The Alta quartz is fairly solid. It is not banded to any extent, and does not show the banded 
structure of the Cromwell lode quartz. Eight crushings of ore are stated to have yielded gold at the 
rate of from 3 J dwt. to 19 dwt. per ton.* 

The presence of scheelite was a source of much trouble in the treatment of the gold-bearing ore in 
the " seventies." At that time it had little or no commercial value, and was looked upon with little 
favour by the pioneer prospectors. 

Scheelite now commands a ready market at high values, and with the improved concentrating 
appliances at present in use, its separation from the quartz gangue is easily and cheaply efiected. 

The prospects obtained in 1874 fully warrant further prospecting on the Alta lode with the \'iew 
of ascertaining the extent of the gold- and scheelite-bearing ore. 



RISE AND SHINE IMPREGNATED SHEAR ZONE. 



This is a zone of crushed schist following a line of shear-fracture that has become impregnated 
with silica containing gold and pyrite. 



llrich. " Geology of Otago," 187.5, p. :iU9. 



To accompany BuHe.tJrvN'I^S.Crcm.weU. StobdivisioTV. Western Otat^oDlv. 




all 



on 



60 J 

run 

the 
slid 

solic 
the 

mile 
lead 



strui 
rate 

the 

favo 

appl: 
of as 



with 



57 

It extends in a south-east course from the edge of the Tarras terrace along the bridle-track leading 
to Tinkers, which it follows across the saddle leading into the Rise and Shine Gull}', the floor of which 
it traverses up to the saddle on the Dunstan divide, whence it passes into Thompson's Creek. Altogether 
it can be traced for a distance of five or six miles, its course being marked by a line of iron-stained and 
broken mica-schist. 

The mineraUsed zone varies from a few feet to 100 ft. wide, but, like most deposits of this 
class, it is ■without distinct walls, although a slickensided sUding surface may be sometimes sharply 
defined. 

The ore consists of country rock in various stages of alteration, impregnated with silica, and in places 
traversed by a network of small leaders and strings of horny quartz. There is no true vein-stone. 
Cubical and arsenical pyrite are always present, and it is due to their oxidation that the rock at the 
surface is so deeply iron-stained. 

The thin quartz veins were found to contain good prospects of fine gold, and this led to a consider- 
able amount of prospecting being done at intervals along the line of outcrop ; and more especially 
near the head of Rise and Shine Creek. But at no point were the results rich enough to form a pro- 
ductive mine. The alluvial wash, however, along the bed of the creek proved highly payable, furnishing 
rich returns of angular gold and of gold with adhering pieces of quartz. 

The shear zone, as we have seen, passes over the Rise and Shine Saddle into Thompson's Creek. 
At one place at Tinkers side, about three miles from the saddle, a shaft was sunk to a depth of 100 ft. 
on a bunch of small leaders, but without meeting with payable results. 

The belt of country in which the shear zone occurs has been denuded to a great depth in Thompson's 
Creek, and it seems not unreasonable to conclude that a large proportion of the gold in the Tinkers 
drifts was originally derived frona this source. 

Genesis of Gold in Shear Zone. — We must first consider the fracturing of the shear zone, and then 
the origin of the mineralising solutions. 

In the absence of igneous rocks in this or neighbouring district, we are unable to connect the origin 
of this zone of fracture with hypogene action. We can only conclude that the crush was the result of 
some tectonic movement, which caused shearing and displacement, resulting in deep fracturing of the 
rocks — so deep as to permit the outflow of mineralised waters, which effected a certain amount of replace- 
ment by silicification and minerahsation by the deposition of gold and iron sulphides, the action being 
hydrotherraal, and somewhat analogous to that so often seen in the waning phases of volcanic 
activity. 

MineraUsed shear zones are at present regarded as unique and rare occurrences. Among the best- 
known examples are the rich gold- and silver-bearing zones at Sonora and Minas Prietas in the State 
of Mexico. 

A better acquaintance with the peculiarities of this class of deposit will probably result in the dis- 
covery that many impregnation bands are of this kind. 

C.4RRICK GOLDFIELD. 

Situation. — This goldfield is situated on the higher slopes of the Carrick Range facing Bannock- 
bum, at altitudes varj-ing from 2,000 ft. to 3,000 ft. above sea-level. The main workings lie at the 
head of Smith's and Pipeclay Gullies, and are reached by a steep cart-road running from the back of 
Bannockburn. 

Discovery. — The angular character of much of the gold found in the gravel wash along the floor 
of Smith's Gully in 1868 and 1869 soon led to the discovery of gold-bearing veins in the vicinity. Lode- 
mining started in 1870, and, with various phases of activity and stagnation, has continued up to the 
present day. Some very rich lodes were worked between 1870 and 1877 ; but the values did not extend 
downward, and the quantity of ore obtainable from the surface stopes was necessarily limited. At the 
present time the field is practically abandoned. 

Rocks. — The lodes occur in the upper part of the Maniototian, and consist of soft argillaceous 
mica-schist, passing in places into phyllite. The easy contours and the rounded outline of the spurs 



58 

bear witness to tlie soft yielding nature of the country rock. The general dip of the rocks is eastward, 
at comparatively high angles of inclination. 

Vein-systems. — The lodes may be grouped into two systems, not in any way genetically diSerent, 
but in accordance with their general strike. Thus we have those which strike approximately north 
and south, and those that run nearly east and west. The latter are sometimes spoken of as cross- 
lodes. 

Carrich Gold-bearing Lodes. 

New Royal Standard No. 1. — This lode crops out about a mile and a half from Bannockbum, near 
the crest of the spur along which the cart-road runs to Nevis. 

The schists on the walls of the lode strike N.-S., and dip east at angles varying from 45° to 65°. 

The strike of the lode is 175°, and the walls are about vertical, having only a sUght inclination to 
the eastward. The lode has been worked by an open trench and underhand stope and by a drive, 
40 ft. lower down, following its course. 

The lode-matter, as seen in the portions still standing, varies from a few inches to two or three feet 
wide. It consists mainly of crushed rock and quartz strings, both much stained with iron-peroxide. 
The walls are irregular and indistinctly defined. 

The lode is crossed by a number of small faults, with clay heads along their course. Many small 
leaders of quartz also cut through the lode at diSerent points. 

Neiv Royal Standard No. 2. — This lies 24 yards west of No. 1 lode. Its course is 155° (true), and 
it is vertical or inclined slightly to the eastward. 

It has been worked by an open cut, short drives, and underhand stopes. The walls are not very 
clearly defined. What appears to be the hanging-waU shows strongly slickensided surfaces. 

The lode-matter consists of rusty- coloured quartz occurring in thin parallel veins, enclosed in 
crushed and decomposed country rock, generally termed " mullock " by lode-miners. 

Both No. 1 and No. 2 lodes appear to occupy lines of fault-fracture. 

Croivn and Cross Lode. — This Lies 3 chains west of No. 2 just described. It has been located by 
shallow pits and open cuts along the outcrop. Its strike is 175° (true). No defined walls are exposed, 
and there appears to be no lode-matter, except a line of rusty-coloured crushed rock. 

On the opposite spur, near the old Caledonia ground, a portion of the lode has been broken out 
in an open cut and underhand stope. In a shallow prospecting-drive, which follows the course of the 
lode in an easterly direction and runs below the open cut, the lode is seen to consist of two small veins 
of rusty-coloured quartz, which run in and out, in places uniting for a short distance and then diverg- 
ing for a foot or eighteen inches. They are enclosed in crushed rock. 

In the stope above the drive the walls of the lode are fairly clear, and often show smooth sUcken- 
sided faces, with a thin layer of compressed clay lying between the wall and lode-matter. 

It is a noticeable feature, and one common to many of the lodes on this and the Beudigo field, that 
the underhand stope, by means of which the ore was beaten out, does not descend to a depth, but 
follows the contoiir of the ground along the outcrop to a depth of 20 ft. or 30 ft. throughout its whole 
length, as shown in the next figure : — 

Tros.pectLTxg IDrvve. 

Old A^ sh^ft ^^.^^fg'j/jjpm^ 




-llChs- 



FlQ. .32. LONGITUDENAl, SECTION OF CkOWN AND CeOSS LoDE, SHOWING DEPTH OF StOPED GeOUND. 

The depth of the stoped ground seems to indicate the extent of the pay-ore in a vertical direction. 



To accompojvy JBidleiirt N° 5, Crom well Suhdiviston,. 




JAMES MACKrNTOSH BELL 
DIRECTOR 



GEOLOGICAL MAP OF 



SURVEY DISTRICT 



- Scale of Chains - 



so 40 



>— < HH 



Refer 



Roads shown Oxua aB=«s===== 

TrcLcka „ „ _ ;;s6--=-'»b«' 

Triaonometrical StaMcna „ >» - C ©iB^i' 

Water Races „ ,, _ -JSti^ — 



Qsology by JoTnesI'Qrh. Topographical data mainly 
supplied, by the Lands a,n/i, Sur-/ey DepartTnent.and 
in pare from original surveys hy A.MFinlayson and 
I^HM^Douall . zaider Jixmes IhrTcs dtrectiorv. 



Reference to Geolo fe ical Colours and Si ^ns ' 



Creek beds end loess Recent ■'.■.:■ 

Bannockburn schist wash Pleistocene 



Kawarau terrace gravels do. 

I Clays, quartz sands and grits,) phocene 
and soft sandstones J" 
Shales . clays, lignites do 

Kakanui Series Upper schists ^-- Paleozoic. 

Maniototo Series Lower schists do. , _ 



Antimony lodes. 
Quartz lodes 



T^ 



Old workings- _ ..,. .., - | Q O n ol 

Sites for boreholes for coal . ® 



Dream ly G.EJSarnj jiug 1907, 



By Authority : John Mackay, Government , 




ine ueubu ui me stuuru giuuuu. occiiio uu im-iiuai/c luc rAtciii/ ui tiii; pay-ure in a vercicai uirecnon. 



59 

The portion of the lode left on the crown of the hill above the stope, and shown in the following 
figure, is probably t}'pical of the character and general arrangement of the lode-matter. 




C ■ '< C 

Fig. 33. Cross-sectios of Ckowx and Cross Lode above Stope near Crown op Hill. 
a. Quartz veins. 6. Crushed rock. c. Mica-schist. 

On the east side of the spur along which the Nevis Road runs, a low-level crosscut has been put 
in for a distance of over 200 ft., at a point 100 ft. below the outcrop. No local information could b ■ 
obtained as to the results obtained in tliis crosscut, which contained too much water to allow an examina- 
tion to be made at the time of the WTiter's visit. Pieces of dense horny quartz found lying on the 
nmllock-tip might be taken to mean that the lode was intersected before driving was discontinued. 

No ground has been stopcd on the east side of the Nevis Road, and, except the aforesaid crosscut and 
one or two shallow pits, no prospecting-work of any moment appears to have been done in this direction. 

The discontinuance of the crosscut may be assumed to indicate that no payable ore was obtained 
at that depth ; and, looking at the character of the lode as disclosed in the stopes on the battery slope, 
it would seem that the construction of the crosscut was a risky undertaking, and one not warranted 
by the prospects. 

In the writer's opinion the line of strike should have been staked out and cuts put in at intervals, 
so as to locate the lode which experience had shown to carry its values near the surface, in no case 
deeper than 10 yards. 

The country rock contiimes the same along the flank of the range, and the indications point to a 
continuance of the lode-formation in that direction. If the lode were located probably runs of payable 
ore would be found in it. 

New Find Lode. — This crops out beside the Nevis Road, about 5 chains west of the Caledonia lode, 
to be hereafter described. Its strike is 150° (true), and it stands practically vertical. The walls are 
well defined, and enclose a vein of compact quartz 8 in. thick, and two broken lines of quartz that may 
at one time have formed continuous veins. 




c & a a & o 

Fio 34. Cross-section of New Find Lode. 

a. Quartz veins. 6. Crushed rock. c. Mica-schist. 

One or two shallow pits have been put down on the outcrop of this lode, but beyond this no attempt 
at systematic prospecting appears to have been made. 



60 



Caledonia Lode.— This lies nearly west of the Crown and Cross lode. It strikes 160° (true), and stands 
vertical. The walls are fairly well defined, and vary from 18 in. to 36 in. apart. The lode-matter 
consists of crushed rock and quartz. 

The outcrop has been worked for a distance of several chains by shallow underhand stopes, reached 
sometimes by a shaft and sometimes by a drive following the course of the lode, or by a crosscut at 
right angles to tjie strike. 




Fig. 35. C-boss-section of Caledonia Lode at Stope passing under Nevis Road. 
a. Quartz veins. b. Crushed rock. c. Mica-schist. 

The Caledonia lode has been located at a point about a chain west of the Nevis Road, but beyond 
this there is no trace of it on the surface. It appears to end suddenly on approaching the steep V-shaped 
gulch in which the battery stands. Its sudden ending is undoubtedly due to its removal by denuda- 
tion from the area now occupied by the gully. 

New Caledonia Lode. — This lode crops out 2 chains west of the Crown and Cross lode. It runs a 
course bearing 145° (true), and is inclined to the westward at an angle of 75°. 

The walls are fairly clean and well defined, the distance between them varjdng from 2 ft. to 4 ft. 

The lode- matter consists of crushed rock, through which there run a few thin veins of quartz. The 
worjc done on the lode comprises trenches and shallow underhand stopes, the latter following the slope 
of the surface down to the bottom of the gorge, a distance of 5 chains. 




Fig. 36. Cross-section of New Caledonia Lode. 
a. Quartz veins. b. Cru.shed rock. c. Mica-schist. 



61 

The character of the lode-filling is well seen in an old stope about 4 chains east of the Battery 
Stream, where a block of ground has been left intact as a pillar to support the stope below. In this 
direction the underlie of the lode changes from west to east, while the strike bends northwards. 



.4G'-- 




FiG. 37. Cross-section of New Caledonia Lode. 
o. Quartz veins. 6. Crushed rock. c. Mica schist. 

The Carricktown Lodes. 

These lodes are situated about 65 chains higher up the Carrick Range, and therefore lie to the 
west of the Caledonia lodes. 

There are three main lodes in this group, and many small cross-lodes and leaders. They crop out 
on both sides of the Novis Road at an altitude of about 3.000 ft. above sea-level. 

The main lodes are known as the Elizabeth, Star of the East, and Heart of Oak. 

The country rock consists of soft argillaceous mica -schist and phyllite, that crumble readily into 
small flakv and splinter\' fragments, and form surface features with smooth or rounded outlines. The 
general strike is about 125^ (true), and the dip 215°, at angles varying from 30' to 40°. 

Elizabeth Lode. — This lode crosses the Nevis Road. It strikes 150° (true), and dips to the eastward 
at an angle of 70°. The chief workings are situated along the outcrop, and consist of an open cut and 
a shallow underhand stope 8 chains long. 

The lode-matter consists of crushed and much-decomposed rock, intersected by thin veins of quartz. 
The width worked out in the open cut varies from 2 ft. to 20 ft. wide. 

At the place where the greatest width has been broken the lode is a network of thin strings of 
quartz, intersecting the rock in all directions, forming a typical " stockwork." 

The foot-wall is fairly well defined. The small interlacing veins mostly come in from the hanging- 
wall, which is not very distinct. 

In a few places the larger of the hanging-wall veins have been followed for some distance by an 
underhand stope. The width of ground broken in the stopes is generally much less than that in the 
open cut at the surface. 

Colleen Bawn Lode. — This lies about 5 chains west of the Elizabeth lode. It strikes north and 
south, and is practically vertical. 

The lode-matter consists of crushed rock and quartz, and nowhere exceeds 18 in. thick. A good 
many crushings were taken out, and are said to have averaged an ounce of gold per ton.* 

From the main shaft on the Colleen Bawn lode there extend two hues of prospecting-pits running 
westerly across the flat grassy spur ; but there is no outcrop to show the nature of the indications that 
led to the work being done. 

Star of the East Lode. — This lode strikes 120° (true), and dips northward at angles varying from 
50° to 55°. It crosses the course of the Elizabeth lode at a point near the crown of the spur lying 
opposite the John Bull spur, and has been worked by trenches and shallow stopes ; but as it is many 
years since mining was done on it, little can now be gathered as to the character of the lode itself. 

* Ulrich. " The Geology of Otago," 1875, p. 219. 



62 

Professor Ulrich reports* that the lode was opened by an adit followang the strike for 480 ft., 
giving 108 ft. of backs under the top of the hill. The ground above the adit was taken out for 
a length of 250 ft. ; while a portion of the lode was removed underfoot for a length of 60 ft. and 
a depth on the underlay of 60 ft., producing 1,200 tons of ore, which yielded gold at the rate of 12 dwt. 
per ton. Going dowoiward the lode-matter became more soUd, and improved in depth. In the portion 
of the lode over the adit the lode ranged from 2 ft. to 8 ft. thick, with an average width of 4 ft., yielding 
14 dwt. of gold per ton. 

The Old Heart of Oak Lode. — This lies about 35 yards east of the Star of the East lode. It strikes 
nearly east and west, and dips northward at angles varying from 55° to vertical. 

The great extent of the open cuts and stopes show that this lode has yielded a large tonnage of 
ore for crushing. In 1875 over 3,000 tons had been raised and crushed'for a yield averaging If oz. 
of gold per ton. 

The ore consists of a number of small veins of quartz and crushed rock, which he in a zone of fault- 
fracture. At one place the outcrop has been broken out for a width of 20 ft. for a length of 3 chains. 

Black Horse Lode. — This was first discovered in a low-level crosscut that was driven to intersect 
the Star of the East lode about 200 ft. below the surface-workings. Its course is east and west, and 
its dip is north at angles ranging from 40° to 45°. It would thus appear to be a hanging-waU branch 
of the Star of the East lode. 

Very little work has been done on this lode, and details of the results are not now available. 

Pifeday Gully Lodes. 

The best-known lodes in this gully are the John Bull, Robert Burns, Golden Gate, Marquis of 
Lome, Kohinoor, and Royal Standard. Work on these has been discontinued so long that very 
little local information is now available, and the data to be gathered among the old workings are 
somewhat meagre. 

John Bull Lode. — This lode crops out near the crown of the spur. It strikes N.W.-S.E., and dips 
N.E. at an angle of 45°. The old workings consist of trenches, shafts, and stopes, and their extent 
would tend to show that the ore was payable for a considerable depth. 

Robert Burns Lode. — This lies near the head of Pipeclay Gully. It strikes 125° (true), and dips 
to the north at an angle of 55°. The walls are well defined, and about 2 ft. apart. Crushings are said 
to have yielded 25 dwt. of gold per ton.f 

Golden Gate Lode. — This lode crops out on the east side of the east branch of Pipeclay Gully, nearly 
half a mile from the crest of the ridge leading into Adams's Gully. 

The schists here strike about N.E.-S.W., and dip S.E. at an angle of 45°. The lode-filling consists 
of crushed rock, traversed by parallel veins of fairly solid quartz from 1 in. to 6 in. thick. 




Fig. 38. Ckoss-section of Golden Gate Lode. 
a. Qiiartz veins. 6. Crushed rock. c. Mica-schist. 



The lode has been worked by trenches along the outcrop, drives, and surface stopes. At the 
mouth of one of the old drives it is seen to be faulted by a well-defined fault, which strikes 65° (true), 
and dips south-east at an angle of 45° — that is, the fault is a thrust-plane running parallel with the 
foliation of the schist. 



• Ulrich: "The Geology of Otago," 1875, p. 213. f Loc. cit, p. 220. 



PLATE XII. 




Cai.kuoma Mink, Cahiik k Uanok. 




ISnUelin So. 6.] 



Geoi.ogicai, Suhvey Cami>, Ckomwei.i, 



[To face p. 62. 



63 

THE GENESIS OF BENDIGO AND CARRICK LODES. 

Immature Replacement Lodes. — A close investigation of these lodes shows that they are what 
might be termed " lode-formations " rather than true lodes. They are mineralised zones of crushed 
rock Ijnng between two parallel lines of fracture. Their main characteristics are so persistent and 
distinctive that they form a type of lode for which the Amter has adopted the name immature 
replacement lodes. 

The chief characteristics of this type are as follow : — 

1. They lie between two parallel fractures, on which more or less faulting has taken 

place. 

2. They traverse the country rock independently of the planes of bedding or foliation. 

3. The lode-matter hnng between the walls consists mainly of crushed rock traversed by 

veins of quartz. 

4. The crushed rock is more or less silicified and replaced by quartz. The extent of replace- 

ment is variable, even in the same lode. 

Commonly the quartz was deposited first along the walls, giving sometimes, as in the case of the 
Caledonia lode on Carrick Range, two opposite, parallel, and contemporaneous veins separated by a 
zone of crushed rock. In other cases the quartz was deposited on one wall only. 

In some places the crushed rock is replaced by vein-quartz from wall to wall, but in all the lodes 
the bulk of the lode-filling is crushed rock, ^\^lere the first conditioix prevails we have what might be 
termed a true quartz vein, and, where the latter condition prevails, a " mullocky lode." Between these 
two extremes we can trace every stage in the evolution of the massive quartz vein ; and in this we 
have a valuable and instructive object-lesson in the genesis of ore-deposits that occur as veins. 

Origin of Minerals. — The veins traversing the crushed rock consist of cr}'stalline quartz, sometimes 
containing a small proportion of scheelite and p\Tite. They generally lie more or less parallel to the 
walls, and are subject to great variation in size and direction, even in a short distance. 

In the blue unoxidized ground the rock and quartz are often brecciated and strongly slickensided. 
It is obvious that wall-movements took place during the formation of the quartz veins. 

At Bendigo the lodes traverse almost horizontal mica-schist, and at CaiTick Range generally 
steeply inclined strata. At both places there is an absence of igneous rocks of any kind. 

The fault-fractures in which the lodes he are local — that is, they have no tectonic or structural 
significance, and in the absence of igneous rocks showing at the surface we can only conclude that 
the fissuring was caused by the intrusion of an abyssal magma that cooled so far from the sui-face 
as still to remain uncovered by denudation. 

The presence of scheelite, the somewhat rare tungstate of lime, at Bendigo, of antimony, at 
Carrick Range, and of cinnabar at Waipori in similar lodes, would tend to support the contention that 
the metalliferous emanations and solutions ascended from below by cracks and fissures connected 
vnth the intrusive magma. 

The formation of a simple fissure, or even of a system of more or less parallel but distant fissures, 
in rocks subjected to tension or shear is easily understood ; but in the case of these lodes we are 
dealing mth twin fissures, enclosing between them a narrow slice of countrj' rock commonly crushed 
and more or less replaced by quartz. 

The mechanics of the stress or stresses that led to this twin fissuring is at present difficult to explain 
satisfactorily. 

The unusual character of the Otago lodes at Skippers, Macetown, and Waipori was noticed by 
Mr. T. A. Rickard* as far back as 1893. He thinks they belong to a type of ore-deposit more common 
than is supposed. 

Age of Lodes. — Of this we have only the most meagre information. It is certain, however, that 
the lodes existed and were subject to denudation during the Pliocene period, since gold-bearing quartz 
derived from them is found in the PUocene quartz drifts. They exist in rocks of probably later Palaeo- 

* Trans. Am. Inst. Min. Eng., vol. xxi, p. 425. 



64 

zoic date, and are undoubtedly older than Pliocene. But we have no data that would assist us to 
ascribe them to any definite period. 

Position of Pay-ore. — The arrangement of the old workings leaves little doubt that the best returns 
were obtained in the upper part of the oxidized zone, at a depth generally less than 50 ft. below the 
outcrop. It has already been stated that rich pay-ore followed the contour of the ground, but did not 
descend vertically to a great depth. 

The ore was not equally rich everpvhere along the outcrop, but no information is now available 
as to the length or pitch of the various pay-shoots. 



Fig. 39. Losgitudi>.-al Section of Lode, showing Depth of Pat-obe. 

Take the following case : Let the above figure represent the longitudinal section of a gold-bearing 
lode. Let the shaded portion represent the depth of pay-ore, and let the top of the hill at a be 200 ft. 
above the hollow at b. 

To say in this case that the lode contained payable ore for a depth of 200 ft. because a is 200 ft. 
above b would be incorrect. For the depth of pay-ore is, relatively to the surface, the same at a as at b. 
If payable ore were proved by a shaft, drive, or crosscut to exist 200 ft. vertically below a, only then 
would it be correct to say that pay-ore lived down to that depth. 

In our example, a drive put in at b on the line of lode would soon run out of the pay-ore. It is 
also obvious that a crosscut put in from the hillside at any point -iO ft. or 50 ft. below the outcrop would 
pass below the rich ore into poor ground. With lodes of this class, long low-level drives and crosscuts 
seldom or never meet with success. The best practice is to keep on, or as close to the gold as the local 
circumstances will permit. 

The manner in which the pay-ore follows the outcrop clearly estabUshes some definite relationship 
between the surface-form of the ground and the zone of enrichment. 

Secondary Enrichment. — The blue unoxidized ore from the deep ground at Carrick Eange was 
commonly lean, being seldom rich enough to pay for working out. In the brown oxidized ground the 
ore was generally highly payable, and, as we have just seen, descended to a certain Umited depth 
below the outcrop, whether on hilltop or steep slope. Hence we have reason to beUeve that the rich 
ore in the oxidized zone is the result of what is termed " secondary enrichment." 

In accordance with this principle it is assumed that as the outcrop of the lode during countless 
ages became worn do^vn by denudation the gold was liberated. A portion of this gold was carried 
into the neighbouring washdirt, while another portion was dissolved by mineral acids, Uberated from 
the decomposition of the contained iron-sulphides, and carried do'miwards in solution through the 
upper oxidized zone, where it was redeposited in the crushed rock and clay, thereby enriching the 
existing lean ore, which thus became payable. 

The precipitation of the gold in this process of concentration presents fewer difficulties since Skey, 
Kohler, and Weed have shown that clay and finely di\aded mineral matter possess the power of absorb- 
ing or extracting metals from their dilute aqueous solutions. 

In secondary enrichment we also have a satisfactory explanation of the circumstance that the rich 
pay-ore follows the contour of the ground along the outcrop of the lodes. 

HAWKSBURN LODE. 

This crops out at three places within a stone's throw of the old Hawksburn homestead. One outcrop 
forms a prominent exposure on the spur above the gate on the cart-road leading down to the flat, and 
another forms a bold spur behind the house. 



65 

So far as one could judge from a surface-examination, the outcrops appear to be isolated blocks 
of quartz or " blows " that follow the foliatiou-planes of the schist. 

The strike or line running between the two main outcrops is 190° (true), and the dip westerly. 

The quartz is grepsh white in colour, and finely crystalline in structure. It is in places crossed 
by many parallel joint-planes, commonly a few inches apart, which impart a platy appearance to the 
outcrop. 

The country rock is a blue silky slaty schist or micaceous slate, passing into phyllite. It strikes 
185° (true), and dips west at angles ranging from 45° to 60°. 

The width of the lode at the northern outcrop above the'gate is about 50 ft. The quartz here has 
a clear vitreous lustre, and shows no signs of slickensides that would indicate movement on the walls 
or in the lode itself. A sample selected at the outcrop showed an assay value of ^ d\\'t. of gold per 
ton. 



'^-SO-^Mi 




Fio. 40. Cross-section of North Outcrop, Hawksbirn Lode. 
a. Lode. 6. Schist. 

A few feet above the hanging- wall of the middle outcrop there is a deposit of graphite, to which 
reference will be made later on. 



JOHN BULL QIARTZ VEINS. 

These crop out on the road to Bendigo, about a quarter of a naile from John Bull Creek. 

No. 1 vein crops out near the Clutha. It .strikes E.S.E.-W.N.W., and dips S.S.E. at an angle 
of nearly 40°. The vein-matter is compact greyish-white crystalline quartz, arranged in more or less 
distinct Jayers Mng parallel with the walls, which are well defined. 

The vein can be traced along the surface for a distance of some 25 chains. Its width at the out- 
crop varies from 2 ft. to 4 ft. 

No. 2 vein crops out 48 yards further north. It varies from 1 ft. to 4 ft. thick, and runs parallel 
mth No. 1 for a distance of some 18 chains. 

The country rock is highly altered and contorted mica-schist belonging to the lower or Maniototo 
Series. It strikes between N.N.E. and N.E., and dips N.W. at low angles that range between 15° 
and 20°. 

Samples carefully selected from these veins gave the following results bv fire assay : — 



No. 1 vein 
No. 2 vein 



16 gr. of gold per ton. 
llgr. 



The relationship between these veins and the foliation of the enclosing rock is shown on the next 



figure. 



2^^r^ ^■"^^^"• 




-^yds--)i S£ 
Fig. 41, Cboss-sectioic showing John Bpil Vbins, 



5 — Cromwell, 



66 

LODES IN BASIN OF ROARING MEG. 

Alon^ the bed of the Roaring Meg, and in all the small branches of that stream, a considerable 
amount of alluvial gold has been obtained. It has been noted that no gold occurs in or above Winter 
Creek. Manifestly the source of the gold lies below the junction of Winter Creek. 

Below that creek the gold found in the bed of the Meg is fairly water-worn, but when the wash is 
followed up into the smaller cfullies the gold becomes rough and vnry, showing that gold-bearing veins 
that have been denuded lie somewhere on the flanks of Pisa Range. 

Two strong veins of white crystalline quartz were located on the flanks of Pisa Range. Samples 
of ore selected from these showed only a trace of gold. 

Henderson's Lode. — Several quartz veins have also been located on the higher slopes of Pisa Range, 
but none of them contain payable ore at the outcrop. Of these, Henderson's lode is the be.st-known. 
It crops out about a mile from the Roaring Meg. high up on the watershed of Mitre or Moonlight 
Creek. The following-up of a trail of rich alluvial gold to the head of the gully just below it led to its 
discovery. 

The lode has not been opened up to any extent ; but as far as could be seen its course is 145° (true), 
and its dip north-east at an angle of 65°. It is about 12 in. wide, and the vein-filling consists of rusty - 
coloured quartz with a distinct comb-structure resembling that of the Bendigo quartz. 

Roaring Meg Veins. — These lie on the broad undulating ridge between the Meg and Gentle Annie 
Creeks, on which Mount Colin and Moimt Gilray are situated. A few prospecting-pits and lines of 
broken quartz on the surface are all that can now be seen. 

No. 1 vein strikes about 160° (true). Its outcrop can be followed for about a quarter of a mile. 

No. 2 vein appears to strike 110° (true). The outcrop can be traced for a considerable distance 
down towards Gentle Annie Stream. 

The quartz in Nos. 1 and 2 veins is in places compact and iron-stained, in others clear and glassy, 
showing a striking development of fine crystals. 

The surface indications would tend to show that the rusty and clear quartz occur in alternating 
shoots. The large amount of quartz lying on the surface would also suggest that these veins are com- 
posed of quartz only, in this respect difiering from the Carrick Range and Bendigo lodes, which are 
composed mainly of crushed rock or mullock traversed by veins of quartz. 

The quartz veins in the basin of the Roaring Meg are merely the trimcated roots of veins that at 
one time stood many hundreds of feet above the present outcrops. In the portions worn away there 
existed the gold which was found concentrated in the gravel wash in the main and branch streams. 
It does not follow that because the gravels were rich that the gold existed in payable quantity in the 
vein from which it was shed. It must be remembered that perhaps tens of thousands of tons of quartz 
were broken up by the natural processes of denudation to peld the thousand or two of oimces of alluvial 
gold obtained in the Roaring Meg Basin. 

At Bendigo and Carrick Range the mullock}- lodes have proved the only payable ones ; and for 
this reason it is advisable for the prospector to direct his attention chiefly to the search for and exploita- 
tion of lodes of this class. 

Silver. 

Small slugs of native silver are reported by Messrs. Swan, Wood, and other allu\'ial miners to have 
been found from time to time with the gold in the washdirt in Lowburn, Five-mile, and other streams 
draining the flanks of Pisa Range. The probable source of this silver is at present miknown. 

Antimony. 

Antimony-ore has been known to exist on the Carrick Range since the early "seventies." In 1874 
a lode was opened out by a Mr. Buchan, who forwarded samples to Dunedin that were found to contain 
from 50 to 54 per cent, of antimony. Since that date several attempts have been made to work the 
lodes, but beyond the breaking-out of some small parcels of ore no systematic development-work has 
been done. 



67 

The present high price ruling for antimony haa once more directed attention to this field, and there 
is now a prospect that something will be done to prove the extent and value of the ore-bodies. 

Buchan's Lodes. — These lie near the top of the range, at the saddle between the north branch of 
Pipeclay Gully and Long Gully. 

The country rock consists of moderately soft flaky mica-schist, passing into phyllite. It belongs 
to the upper part of the Maniototo Series, and, being less altered than the Bendigo schists, is not easily 
distinguished from the upper schists. 

No I lode crops out a few chains south of the saddle. It strikes 75° (true), and dips northward at 
an angle of about 45°. The lode-matter as seen in the prospecting-hole on the spur consists of crushed 
rock a foot or two wide, with an irregular streak of quartzose antimonite on each wall. The walls are 
well defined, the hanging-wall showing slickensided surfaces. 

The ore-veins on the walls vary from 1 in. to 3 in. thick ; and carry a considerable proportion of 
antimonite and cervantite, the yellow oxide of antimony. Very little prospecting has been done on 
this lode. 

The relative positions of Nos, 1 and 2 lodes are shown in the next figure. 



ITiZ 




Fig. 42. Cross-section .showing Buchan's Anti.mony Lodes on Caerick Range. 



No. 2 lode crops out about 3 chains south of No. 1 , on the steeply rising ground. It appears on 
the surface in several places, and has been worked to some extent by trenches and underhand stopes. 

In the underhand stope, 3 chains from the boundary-fence, the walls are from 2 ft. to 4 ft. apart, 
but no ore is to be seen, the lode-matter in the portion left standing consisting mainly of clay and 
crushed rock, with a little of the yellow oxide of antimony .scatt red throughout. At this place the 
lode is cut ofi sharply by a small thrust-plane, showing a horizontal displacement of about 4 ft. 

Lying on the mullock-tip there are numerous pieces of antimonite and cervantite, mostly quartzose 
and low-grade. 

No work appears to have been done on Buchan's lodes for some considerable time. 

Horn's Lode. — This lode crops out on the flat spur at the head of Shingly Gully, one of the branches 
of Long Gully. At the time of the writer's vi.sit in January, 1907, it was being opened up by a shallow 
trench along the strike. From a cut 8 ft. long and 5 ft. deep about 2 tons of ore had been extracted. 

The lode runs 75° (true), and stands vertical. The ore occurs as detached masses, from a few inches 
to 30 in. wide. The remainder of the lode-filling is crushed rock and clay. 

The north wall is fairly well defined. The other wall is indistinct. 

At the east end of the trench the lode throws off a small branch lode bearing 105° (true). Of the 
extent and value of this lode nothing was known in January. The ore in the main lode consists of 
antimonite and cervantite in a matrix of quartz. The antimonite occurs in more or less rounded 
masses that are easily hand-dressed up to a fairly high-grade product. Much of it is, however, 
intimately associated with quartz, and cannot be handled at a profit. 

The walls appear to be coming together in the bottom of the trench, but they may possibly widen 
out lower down. 

A parcel of 7 tons of hand-dressed ore is said to have been shipped to Australia in April of this 
year. 

5* — Cromwell, 



68 

A sample selected from the 2 tons of ore lying on the grass in January, analysed by Dr. Maclaurin, 
Grovernment Analyst, gave the following results : — 

Antimony . . . . . . . . . . . . 46'2 per cent. 

Equivalent to antimony -sulphide . . . . . . . . 64"68 „ 

Gold .. .. .. .. .. .. .. 21 grains per ton. 

Silver . . . . . . . . . . . . . . 9 ,, 

Horn's lode has been found cropping out at several places, going both east and west along the 
strike, and in one or two places the surface prospects are said to be very encouraging. 

It should be mentioned that antimony lodes are notoriously patchy in all parts of the globe. 
Strong, well-defined, continuous bodies of this ore are practically unknown. Therefore, to prove the 
extent of the ore-body it is necessary to open out a large area of ground ; and, in order to maintain 
the mine as a going concern, development-work must be kept well ahead of the stoping requirements. 

The surface prospects obtained on the flat spur at the head of Shingly Gully are sufficiently 
encouraging to warrant the systematic prospecting of the ground being undertaken. In such a situation 
prospecting will necessarily be expensive, but the ore obtained should at least pay part of the cost. 



Fia. 43. Showing Cross-section of Horn's Antimony Lode. 
a. Crushed rock and clay. b. Blocks of antimony-ore. 

Small veins of antimony-ore have been located on the western' slopes of Mount Difficulty, and on 
the face of the steep spur leading down to Doolan's Creek behind Victoria Bridge, but until they are 
opened up nothing can be said of their value and extent. 

Asbestos. 

The serpentine dyke near the head of Springburn Creek contains small, irregular, matted masses 
of asbestos of poor quality. 

The bulk of the asbestos of commerce is chrysotile, which occurs in distinct veins in serpentine. 
The fibre of chrysotile is very fine, and lies at right angles to the plane of the vein. There appears to 
be no chrysotile present at Springburn, and the fibrous amphibole that was the object of the pro- 
specting operations some nine years ago does not appear to occur in sufficient quantity to be of com- 
mercial value. It is of poor quahty, and could only be used for the manufacture of fossil meal and 
asbestic packing. 

Graphite. 

This occurs intercalated in the schist a few feet above the hanging-wall of the Hawksburn lode 
in the Bannockburn district. It has been prospected by a shallow pit about a chain north of the 
middle outcrop of the lode. The sides of the pit have fallen in, and, except the debris at the pit-bank, 
nothing whatever can be seen of the graphite in situ. 

The rock is a micaceous slate that passes into phyllite. It strikes nearly north and south, and 
dips west at an angle of 60°. 

There is no appearance of graphite immediately to the north and south of the pit, from which we 
may conclude that the deposit is Umited in linear extent, 



69 

The graphite hnng on the pit-bank is quartzose and of poor quality, but naturally the best would 
not be left behind by the prospectors. It is impossible to say what the prospects are from a surface 
examination, but the lack of linear extension does not give much hope of finding a large deposit. ' 

The relative positions of the quartz lode and graphite are shown in the next figure. 



Fig. 44. Showing Graphite Outcrop at Hawksburn. 
a. Graphite. h. Hawksbum lode. c. Micaceous slate. 

Co.^L. 

The coal of Central Otago is a lignite, which occurs at or near the base of the Pliocene Series of 
fresh-water beds that occupy the floor of the old lake-basins. 

In the Cromwell basin the lignite crops out along the banks of the Kawarau between Cromwell 
and Bannockburn. The line of outcrop also runs some distance up Shepherd's Creek, following the 
margin of the old basin. 

Between Dcadman's Point and Quartz Reef Point the lignite lies below flood-level, but has been 
located by dredges and by boreholes. 

Along the Cromwell side of the basin the lignitic measures dip towards Pisa Range at low angles, 
but rise again sharply along the foot of the range, thus forming an unsynimetrical syncliue. 

The hgnite commonly occurs in two seams, the lower and larger of which has been worked at various 
places ; but on the banks of the Kawarau, a mile below the junction of the Bannockburn, the lignite 
is split up into a number of small unimportant ^eams. 

In a country so entirely destitute of forests or native vegetation suitable for fuel the lignite has 
been an inestimable boon not only for domestic necessities, but also for the supply of motive power, 
without which the evolution of the modern steam-dredge would have been set back a century. 

Excelsior Coal-mine. 

This is situated on the north bank of the Bannockburn, about half a mile from the junction of 
that stream with the Kawarau. 

The lignite crops out a few chains east of the main incline, from which the mine is worked, and 
strikes about north and south. It dips west at an angle of about 10°. 

Three seams are seen in going down the imline — namely, two near the surface and one at the 
bottom. The upper seams arc 18 in. and 5 ft. thick respectively. They are separated by a bed of 
fireclay from 2 ft. to 3 ft. thick. 

The main seam is about 7 ft. thick, and contains some 5 ft. 6 in. of workable coal. It is remarkably 
free from shakes and faults, and maintains a uniform thickness over a length of nearly three-quarters 
of a mile. 

The analysis of a sample of this lignite made by Dr. Maclaurin, Government Analyst, gave the 
following results : — 

Fixed carbon . . . . . . . . . . . . 3098 

Hydrocarbons . . . . . . . . . . . . . . 3986 

Water .. .. .. .. .. .. .. 2254 

Ash .. .. I* 6-62 



10000 



Total sulphur . . . . . . . . . . . . . . 0*51 per cent. 

Evaporative power . . . . . . . . . . 4 lb. 



70 

This Hgnitr" is most'y usf^d on dredges for steam-raising. It is sold at 12s. per ton at the mine. 
This price includes the uso of the sacks in which the coal is placed for transport. 

The scam being worked is overlain by thin-banded sandy clays, which in places contain numerous 
casts of a fresh-water bivalve resembling those found in the Maniototo basin. 

A feature of this coal, and one not often seen in New Zealand, is a very distinct vertical " cleat " 
or series of cleavage-planes lying close together, which traverse the seam at right angles to the plane 
of the strike — i.e., they run parallel with the direction of the dip, forming what in England would be 
termed " butt cleat." 



ScLnnodkhum. 
ExceZsLor Mxne 




Fig 45. Showing Section across Bannockburn. 



a. Creek-bed gravels, mostly tailings. 
d. Soft sandstones and clays. 
g. Quartz drift (gold-bearing). 



h. Bannockburn schistose drift. c Sandstone and schist drift of Kawarau. 

'. Fireclays, clays, and sands, with seams of lignite. /. JIain seam of lignite. 

h. Upper schists (Kakanui Series). i. Lower schists (Maniototo Series). 



Shepherd's Creek Coal-mine. 

This coal-mine, of which Mr. A. S. Gillanders is manager, is situated on the west side of Shepherd's 
Creek, about a mile from Bannockburn. It is worked by an incline, which fol'ows the underlie of the 
seam of lignite in a westerly direction. The inclination of the seam is not uniform, varying in different 
places from 1 in 4 to 1 in 3. 

About 600 ft. from the surface the seam rolls gfently over and dips away to the south instead 
of the west, a circumstance which has caused a good deal of trouble in the construction of the 
roadways. 

The seam varies from 7 ft. to 15 ft. thick. Passing towards the north, at a point some 4 chains 
from the incline, a thin parting of clay appears in the coal, which thereafter in this direction becomes 
divided into two distinct seams. The lower coal only is worked. 

In this direction the seams are crossed by several small faults, along which the coal is so crushed 
and broken as to be of no value for market purposes. 

Going south of the incline the seam shows only the track of the parting which divides the seam 
going north. Both north and south of the incline the seam decreases in thickness. 

The coal at this place is underlain by stiff clay of unknown thickness, and overlain by a bed of 
clean quartz sand from 20 ft. to 30 ft. thick. This sand is very fine, except in one or two places where 
the lower part is gritty. When broken into in the roof this fine drift runs like a quicksand. 

This lignite is of better quality than the Bannockburn lignite, and is largely used for domestic 
purposes. 

A sample analysed by Dr. Maclauriu gave the following results : — 



Fixed carbon 
Hydrocarbons 
Water , , 
Ash 



32-60 

39-90 

22-20 

5-30 



Total sulphur 
Evaporative power 



100 00 

0-32 per cent, 
4-24 lb. 



7b accompcuLy SjUletirvN^'S, Croiiiw^l Sid}diy^isi<t7h}^sterTv Otago I)ivisioTi. 





Geological Map of 

INJ C0ALFIJELOS, 
CARPIIJ€K\ OOLOFIJELD. 

Bannockburn and Cromwell Survey Districts. 

Scale of ckains 



Qeology iy James I^irh 
TbpogrophicnX. daXa, Tncajriby sullied- ty 
t?te Lands and- Surv^ Z>^tartm,ent, and, 
ifh -part -frortv oriffinaZ surveys TivA-Gordonj 
Macdon.ald.AM.FLrxia.ysan. a^dr BM'^ounR, 
under Jdrnes Parks dzrectLorv. 



- Reference 



. shown thus c 



40 20 



Roads 

120 Tracka ,, _- „- '=--^ 

^ TrigoTwm^trical Stations — „ » - C @i8fi' 

Water Races »; n- Jf^^ 



Reference to Geological colours 



RECLNT PLEISTOCENE 



PLIOCENE 

Manuherikia Seri 






Drawn by G.EMaiTti . Scptr ISO? 



Zodes OeehBeds Banrux^zbum. Kawaraxo Cement CLays. Shales. Qu/u-tzQrU^ 

oTuiXoess Schist TerrcLce Stones Quartz sands stt^rtis. Clays. (Qrrznxte Was?)^) 

Wash- QrxLveis ^ Soft Sandstones Lignites 



PALEOZOIC 

Kakanui Maniototo 
Series Seri 

o QqI 

Lower Old, Sites fbr 

Schists HB^AiTiys Boreholes 

fbr CoaJ, 



71 

This lignite contains less sulphur, water, and ash than the Bannockburn lignite, and a higher per- 
centage of fixed carbon. 

Roaring Meg Coal. 

A small basin of coal occurs in the lower end of Plankbum, at an altitude of 2,600 ft. above the 
sea. The same coal can be traced into the Tinselburn going south, and to the top of Queensberry Range 
going north, its strike being nearly north and south. 

The seam has been opened at several places in the Piankburn basin, but very little can be seen 
of the coal, as the old trenches have fallen in, and no definite information could be obtained locally 
as to the thickness. 

A sample selected at the outcrop showed the following composition (analysis by Dr. 
Maclaurin) : — 



Fixed carbon 
Hydrocarbons 
Water 
Ash 



41-80 

37-31 

17-12 

3-77 



Sulphur 
Evaporative power. 



100-00 

1 -82 per cent. 
5-43 lb. 



The analysis shows this to be a brown coal of fairly good quality — by far the best in Central Otago, 
and much superior to the lignites of Cromwell basin. 



Queensberry R^nge 



Plant- burr) Pi'sj Range 

Roarir,£ Meg 

h 




Fio 5. Section across Plankbdrn. 
a. Lacustrine bedH. b. Mica-schist. 



The manner in which the lacustrine beds are nipped up along a fault-dislocation is well shown in 
the above figure. 



Gibbstan Coal-mine. 

The old mine is situated on the flank of the range some 900 ft. above the Kawarau River, and 
2,100 ft. above the sea. 

The coal-measures occur in a stretch of broken slipping ground that extends towards the saddle 
. leading to Doolan's Creek. 

The seam of coal is overlain by fine grey sand, and underlain by bluish-coloured fireclay. 

The coal was stripped by sluicing, and worked out for the most part by open faces The old 
workings cover altogether an area of 1^ to 2 acres. 



72 

The coal-measures run up to the saddle to the present mine at an altitude of 3,300 ft. above the 
sea. Here the seam is from 20 ft. to 30 ft. thick, and dips towards the schist. The coal-measures lie 
in broken faulted ground that forms a big slip, clinging to the flank of the range. 



Gibbston Saddle 




Fig. 46. Showing Coal-seam at Gibbston Saddle. 
o. Broken rock in slipped ground. h. Seam of brown coal. 



c. Schist. 



The composition of the Gibbston coal is as follows (analysis by Dr. Maclaurin) 

Fixed carbon 

Hydrocarbons 

Water . . . . . . . . ^ . . 

Ash 



Sulphur . . 
Evaporative power 



35-86 
40-87 
20-60 

2-67 

10000 

037 per cent. 
4-66 lb. 



The proportion of ash in this coal is remarkably low for a brown coal. The sulphur is also below 
the average. 

The Gibbston coal can be traced do-vni to Doolan's Creek, although not in a continuous stretch, 
as a wide gap exists between the saddle and the creek. 

Some prospecting has been done on the coal on the west bank of the stream, but as all the work- 
ings have fallen in there is no means of judging the extent or thickness of the seam. 

A sample of Doolan's Creek: coal selected at the outcrop gave the following results when analysed 
by Dr. Maclaurin : — 



Fixed carbon 
Hydrocarbons 
Water 
Ash 



19-13 

66-24 

5-81 

8-82 



Sulphur 



10000 
0-40 per cent. 



This coal shows an extraordinary development of the hydrocarbons at the expense of the fixed 
carbon. It is said to be a very superior household coal. Its high percentage of hydrocarbons should 
make it valuable for gas- making purposes. 



Cardrona Coal-mine. 
Here we have the unusual spectacle of a patch of coal-bearing strata perched on the top of a high 



spur. 



fatjl-j 



fli'h 



',\',\.V 



^ 



OJ 



ftu?. . 




73 

The seam of coal is about 12 ft. thick, and is first stripped and then worked back as an open face, 
resembling a railway-cutting in course of excavation. 

The seam, or that portion of it now being worked, is lying horizontal between two faults, as shown 
in the next figure : — 




Fio. 47. Shdwinq Section of McDouoall's Cabdbona Coal Pit. 
o. Unknown. b. Clay and soil. c. Bluish clays. d. Yellow and grey clays. e. Mica-schist. 

The width of the coal-face varies from 30 to 40 yards. The height above sea-level is about 
3,500 ft. 

An analysis of this brown coal by Dr. Maclaurin gave the following results : — 

Fixed carbon 
Hydrocarbons 
Water 
Ash 



. 30 45pe 


r cent 


. 4100 


>> 


. 18 70 


» 


. 9 85 


>> 


100 00 


>» 


. 0-66 





Total sulphur 

This coal is a remnant of the old narrow lake-basin that extended at one time from the Roaring 
Meg to Cardrona, and from the Cardrona to Gibbston and Doolan's Creek. 



Artesian Water in Central Otago. 

In the region included within the dry belt of Central Otago the question of water-supply is of 
supreme importance. There are many mountain-streams that could provide a bountiful supply of 
water if the capital were availabe for the construction of the hydraulia works necessarj' to convey the 
water to the user. But the settlers are not always able to obtain the capital required ; and in many 
cases the cost of bringing in the water would load the land with charges beyond its producing-power. 

Underground water is another probable source of supply that has not received the attention that it 
deserves, and for this reason the writer during the past two summers spent some time in collecting such 
data as would enable him to form an opinion as to the existence of artesian water in the old lake-basins 
of Central Otago. 

The Maniototo, Manuherikia, Ida Valley, and Cromwell plains are old lake-basins filled with a 
great succession of lacustrine deposits ; and the questions that call for investigation in connection with 
an artesian water-supply are as follows : — 

(a.) Are the strata of such a porous character as to be capable of storing large volumes of under- 
ground water ? 

(b.) Are the strata so arranged that the stored water exists imder sufficient pressure to rise to the 
surface in artesian wells ? 

The lower strata of the lacustrine series consist of loose quartzose sand and gravel drifts that are 
followed by shales, and clays with seams of lignite, sandstones, and quartzose drifts. 

The lower strata are capable of storing large volumes of underground water ; and the shales, clays, 
and sandstones should be sufficiently impervious to retain the water under pressure if the strata them- 
selves are so arranged as to effect that purpose. 



74 

The most favourable arrangement for water-bearing strata to assume for the supply of artesian 
water is the synclinal or trough-like form, and when strata are so disposed, in the absence of disloca- 
tions or low-lying outcrops from which the underground water could drain by gravity, the existence 
of artesian water is practically certain. 

We find that in all the old lake-basins of Central Otago the lacustrine beds are tilted so as to form 
synclines or troughs, the axes of which run parallel with the length or greatest linear extension of the 
basins. Such troughs must be full of underground water, and in the absence of dislocations or low- 
lying outcrops the water should exist under pressure. 

The plains in the old lake-basins are mostly covered with recent and Pleistocene detritus, and for 
this cause they are not often seen except along the margin of the basins. 

The only places where exposed outcrops exist are at the lower ends of the basins in all cases near 
the boundary of the lacustrine beds and the schists. At such places the water would escape by gravity, 
but at or near the centre of the basins all the conditions are favourable for the existence of artesian 
water. 

For example, there is little prospect of finding artesian water near the Kawarau between Cromwell 
and Bannockbum, or in similar situations near Alexandra. There is, however, ever}' reason to beUeve 
that artesian water will be foimd by boring on Cromwell Flat, near the Hospital or racecourse. 

In the absence of exact data it is impossible to say how deep the water-bearing drifts lie at these 
places. This will depend on the depth of the old lake-basin, on the floor of which the lacustrine beds 
were laid. If we judge from the thickness of strata exposed in the old tail-races above the Chinese 
camp at Cromwell , and the angle of dip, the depth is not likely to be less than several hundreds of feet. 
It may be 300 ft. or perhaps less if a ridge of schist is struck, but it may very well be 500 ft. or 600 ft. 
If water is struck, as the prospects fully warrant, the results would more than compensate the cost of 
boring the well. 

Artesian water should be found in the Manuherikia basin between Omakau and Matakanui — let 
us say, near Laidlaw's station ; and anywhere in the centre of Ida Valley. 

In all cases the wells should be sunk imtil the lignite measures are passed through. 




o 



•-5 



^ 



ea 




01 



PLATE XV. 




Bannockbukn, and Cldtha Valley. 



Bulieiiil No. 5." 



[fo fact p. 7| 



16 





CHAPTER 


V. 




PETROGRAPHY. 




Metamorphic Rocks 


I'age 
. 75 


Detrital Igneous and altered Rock 


5 — coitlinmd. 


Epidotizecl Clilorite-schist 


. 7'. 


Biotite-granite 


.. HI 


Quartz-chlorite-schist, with Elpidote 


7") 


Augitc-hypersthene-diovite 


.. 82 


Micaceous Quartz-schist 


. 70 


Augite-diorite 


.. 82 


Chloritic Quartz-schist 


. 7« 


Hornblcnde-si-hist 


.. 82 


Micaceous Quartz-schist 


. 7<) 


Hornblende-diorite 


83 


Granular Chlorite-schist 


. 77 


Hornblcndc-caniptonitc 


.. 83 


Schistose Greywacke . . 


. 78 


Pink Quartz-Schist 


.. 84 


ftOca-schist . . 


. 78 


Detrital .Sedimentary Rocks 


.. 84 


Altered Greywacke 


. 78 


Greywacke . . 


.. 84 


Serpentine 


. 79 1 


Greywacke . . 


. . 85 


Detrital Igntious and altered Rocks 


. 80 


Greywacke . . 


. . 85 


Hyperstlienc-dioritc 


. 8(t 


Gre3nvacke . . 


. . 85 


Feldspar-porphyrite 


. 80 


Sandstone 


.. 85 


Mica-gneiss . . 


. 81 







Metamorphic Rocks. 
74. Epidotized Chlorite-schist. — Occurs as a band interbedded with quartz schist on the 
eastern flanks of the Pisa Range and the we-steni flanks of the Dunstan. 

Macroscopic Examination. — S.g., 313. A greyish-green rock, with frequent foliao of quartz 
and of dark-green epidotized chlorite. Octahedra of magnetite are common, and often very coarse 
and thickly developed. 

Microscopic E.xamination. — The rock consists chiefly of green chlorite, with a considerable 
development of epidote, a small quantity of quartz, and a notable proportion of magnetite. 

Chlorite : Occurs in fibres and bunches of fibres, occasionally with a rough radial grouping. The 
colour is bright green, or yellow by serpentinization. With this alteration, a large quantity of secondary 
magnetite separates out, in strings and elongated particles, often forming a selvage to a patch of the 
altered mineral, which becomes very dense. 

Quartz : This is fine-grained, not conspicuous, and quite subordinate, except in occasional coarse 
lenticular folife. 

Epidote : An alteration-product of chlorite by dynamic processes ; is abundant in pale-yellow 
elongated crystals, often with a sheaf-like or crossed arrangement of individuals. 

Rutile : Occurs in small needles and granules, highly birefringent. 

Magnetite : Very abundant as an alteration-product. Some primary magnetite is present, in 
well-shaped hexagons and squares, frequently very coarse. 

77. Quartz-chlorite-schist (with Epidote).— This occura associated with the epidotized 
schist of the Pisa and Dunstan Ranges. 

Macroscopic Examination. — S.g., 2-78. A fine-grained green rock with a micaceous shimmer, 
and a considerable development of quartz in uniform thin laminae. Fine-grained magnetite is frequent, 
and larger octahedra also occur. 

Microscopic Examination. — A mosaic of elongated quartz granules, in which are set bands of 
chlorite fibres. 

Quartz : The individuals are markedly elongated in the direction of foliation, and frequently have 
irregular extinction. They contain numerous liquid inclusions as well as inclusions of rutile. 

Plagioclase : A little feldspar that may be oligoclase is present in small clear plates. 

Chlorite : Occurs in bands of green fibres lying along the foliation-planes. It is highly altered, 
with the formation of the products noticed below — magnetite, epidote, and calcite. 

Magnetite : Occurs as a primary constituent in good angular crystals, as well as a secondary pro- 
duct, in irregular grains, derived from the chlorite. 



76 

Epidote : Occurs, like magnetite, as an alteration-product of chlorite, in elongated crystals and 
granules. 

Calcite : Is present in irregular patches, a product derived from chlorite. 

Remarks. — The most conspicuous bands in section are of magnetite and epidote, both in elongated 
granules, with residual chlorite, and a few bauds of less altered chlorite. Deep-seated metamorphism 
of an original quartz-chlorite-schist has resulted in the marked development of epidote. 

93. Micaceous Quartz-schist. — This rock forms the country rock of the Bendigo reefs. 
Macroscopic Examination. — S.g., 2-81. Quartz occurs in both coarse and fine fohse, and mica 

shines conspicuously along the foliation-planes. The rock is intersected by veins and stringers of 
quartz up to h in. in wdth. It is frequently highly phcated, and the plications cross the fohation- 
planes almost at right angles. 

Microscopic Examination. — The rock consists essentially of quartz, with pale dusty muscovite 
in smaller proportion. 

Quartz : Occurs in elongated granules of various sizes, showing distinct foliated arrangement, and 
marked irregular or cloudy extinction. The individuals contain inclusions of rutile and dust, generally 
arranged in lines parallel to the foliation-planes. 

Muscovite : This is sericitic mica. It occurs in patchy bands of scales along the foliation-planes. 
The individuals are long and slender, chloritized and iron-stained. Some of the chloritic material, 
however, appears to be original. 

Magnetite : Is fairly common in small octahedra and granules. 

Plagioclase : Is present in small quantity. 

Rutile : A few small granules occur. 

Epidote : A small quantity is present, in pale-yellow elongated crystals. 

94. Chloritic Quartz-schist. — This rock occurs as a band in the Carrick Range, forming 
the country rock of the Caledonian group of lodes. 

Macroscopic Examination. — S.g., 2-76. Compared with the Bendigo rock, the quartz fohse are 
finer and more imiform. Cross-plications occur, but to a much less extent. The micaceous material 
has a greenish shimmer, and dark-green strings, due to the development of magnetite and epidote, occur 
frequently between the quartz folise. 

Microscopic Examination. — The rock appears in section as a mosaic of elongated quartz particles, 
with an even distribution of chlorite fibres. 

Quartz : In elongated or rounded granules, with irregular extinction, and containing needles and 
grains of rutile. It forms the main mass of the rock. 

Chlorite : Is pretty evenly distributed, in pale-green fibres. The individuals show a very regular 
elongation along the foHation-planes. They are somewhat decomposed, with separation of a little 
epidote and dusty magnetite, and with iron-staining. 

Magnetite : A few granules are present. 

Rutile : Is common in needles and grains, generally included in quartz. 

Plagioclase : A few twinned plates occur. 

Epidote : Is associated with secondary magnetite, as an alteration-product of chlorite. 

Remarks. — This rock, although more quartzose than the typical chlorite-schists, shows the same 
alteration-products of its chlorite. The metamorphism is, however, less complete, as imaltered 
chlorite is present in larger proportion. 

97. Micaceous Quartz-schist.— Occurs on the south-western slopes of the Dimstan Range. 

Macroscopic Examination.— S.g., 2-73. A fissile rock, foliated evenly with quartz, and with 
a micaceous shimmer along the foUation-planes. 

Microscopic Examination. — A mosaic of irregular quartz granules, through which are scattered pale 
needles of mica, and needles and granules of epidote, with some rutile, in bands along the foliation-planes. 

Quartz, in irregular grains, forms the mass of the rock. The grains show cloudy extinction, and 
are aot markedly elongated. 



PLATE XVI. 







1 Ki'ii)otizi;d Ciii.oiaTK-scniJfT, Eastern Fla.vkk Pisa Rakge. Oidiiuirv liylit. 

2 Chi.oiutic (^LAiuz-scHisr FiiOM C'AituicK KA.\(iE. Porali/A'il li-rlii. 

"5 CHAMI.Al! ClILOIilTE-SCHIST, GlBB>TON. Poliuizcd light. 

4. Mica-schist, Chomwkll. Polarized light. 



.\11 magnified :J() titiies. 



Ilnlletin No. .5.J 



[To face p. 76 



77 

Mica : Occurs as pale slender blades of muscovite, not in large quantity- Where it is at all bunched, 
the individuals are chloritized and iron-stained. 

Epidote, granular and elongated, is common in bands and clusters along the planes of foliation. 

Rutile : A subordinate quantity, in roimded grains and needles, occurs in association with the 
epidote. 

Remarks. — This rock contains a considerable quantity of epidote, which is not, in this case, an 
alteration-product of chlorite. 



1. Granular Chlorite-schist. — Occurs in bands at several places in the neighbourhood of 
Gibbston, notably near the Kawarau Bridge between Gibbston and Arrow. 

Macroscopic Examination. — S.g., 2-91. A dark-green rock, schistose, but ^\^thout a marked 
development of quartz foliae. The rock is studded with small granules of quartz, which stand out 
on the rough surface. 

Microscopic Examination. — In section the rock is composed of plates of binary- plagioclase and 
quartz. The interspaces are occupied by chlorite, while epidote and rutile are both prominent. 

Quartz : The crystals are fairly large, generally polygonal, sometimes elongated, in section. The 
edges are somewhat corroded, but the individuals are not crowded close together or interlocked. 
Irregular extinction is not marked. 

Plagioclase : Fairly abundant ; occurs in large plates showing binary twinning. 

Chlorite : Occurs in light-green rectangular plates without ver\' marked elongation. The aggregates 
of chlorite wrap round the quartz granules. It appears to be chiefly an alteration-product of horn- 
blende, of which a few residual cores may be seen. 

Calcite : Occurs in long highly brrefringent plates with polj-synthetic t\vinning. These are evi- 
dently of secondary' origin. 

Epidote : Granular to needle-shaped in habit ; this constituent is very common. It originates 
in the chlorite, where it occurs thickly, but it is also very prominent in the (juartz. Here it has two 
modes of occurrence — (a) in lines along the borders of the quartz granules, and (b) with an irregular 
concentric arrangement. 

Rutile : Is fairly common as small granules in the quartz. 



Analysis 
Silica (SiO 2) 
Alumina (A1203) 
Ferric oxide (FejO.,) 
Ferrous oxide (FeO) . . 
Manganoui o.xide (MnO) 
Titanium-oxide (TiOj) 
Lime (CaO) 
Magnesia (MgO) 
Potassium-oxide (KjO) 
Sodium-o.xide (Na20) 
Sulphuric anhydride (SO3) 
Carbonic anhydride (CO 2) 
Water lost below 100'' C. 
Water lo.s-t above 100° C. 

Total 



by A. M. Finlayson, M.Sc. 



.■59-91 

10-22 

1312 

7-26 

0-39 

2 06 

12 09 

2-26 

2-57 

3-41 

401 
0-23 
1-80 

99 -.33 



Remarks. — This is an intermediate tj^pe of chlorite-schist, less markedly schistose than those 
of the Dunstan, characterized by their striking development of epidote and magnetite. The nature 
of the quartz, the derivation of the chlorite, the quantity and habit of the plagioclase and epidote, all 
point to an igneous origin for this rock, With further alteration of the chloiite, the rock might be 
plassed almost as a granulite. 



78 

2. Schistose Greywacke. — This rock occurs below the Bannockbum lake-beds, and crops 
out along the fault-liue on the east flank of the Carrick Range, and also on the western slopes of Cairn 
rauir, up the Hawksburn. 

Macroscopic Examination. — S.g., 2-72. The rock is dark broAvn in colour, and arenaceous in 
texture, although it contains bands of a silky or argillaceous character. It has the appearance of a 
true gre}'wacke, except for a ready cleavage along the bedding-planes. 

Microscopic Examination. — The rock consists of fine quartz granules imbedded in a very fine- 
grained aggregate of decomposed and iron-stained matter. 

Quartz, in irregular granules, is the chief constituent, but is less prominent than in the detrital 
pebbles of greywacke examined from the Kawarau River. The arrangement of the individuals along 
the foliation- or cleavage-planes is, however, more marked. 

The remainder of the rock consists of fine-grained matter, largely decomposed ^v-ith the separation 
of iron-oxides. Occasional residual feldspars and some sericite may be distinguished, as well as kaolin 
and some grains of magnetite 

Remarks. — The rock is t\'pical of the Kakanui Series, intermediate in metamorphic character 
between true slates and greywackes on the one hand and true mica schists on the other ; but the 
Hawksburn rock is more closely allied to the greywackes than to the schists. 

3. Mica-schist. — Occurs at the Double Cone and on the adjacent ridges. 

Macroscopic Examination. — S.g., 2-71. A fine-grained rock, in appearance a phyUite, generally 
evenly foliated with quartz in coarse or fine laminae. A much less altered rock than the mica-schist 
of Cromwell. 

Microscopic Examination. — The rock consists of an aggregate of small quartz granules, with 
parallel bands of iron-stained micaceous and chloritic matter. 

Quartz : The granules are small, numerous, and irregular in shape, and compose the mass of the 
rock. The individuals are generally elongated along the foliation-planes, and contain inclusions of 
rutile needles. 

Chlorite : This occurs in pale-green plates and fibres, generally elongated, and disposed throughout 
the mass of the rock without being confined to distinct bands. 

Altered and decomposed Folia : These appear originally to have been chlorite, the rock being a 
chloritic schist, but they are now obscured by the development of calcite and sericitic matter, and by 
much iron-staining. 

Plagioclase : A few twiimed plates occur. 

Epidote : Is present as small needles scattered through the rock. 

Rutile : Occurs occasionally, in granular or knee-shaped individuals. 

Remarks. — This is another type of the semi-metamorphosed rocks. Its difference from the 
Hawksburn rocks lies in its more quartzose appearance and greater development of quartz folise. 
This is doubtless due to local differences of sedimentation in the original rocks. 

4. Altered Greywacke.- Occurs in association with the previous rock. 

Macroscopic Examination. — S.p, 2-70. A greyish rock with the texture of a sandstone, but 
schistose in structure and containing folise of quartz. 

Microscopic Examination. — In section the rock is an aggregate of elongated quartz granules, 
with close-set parallel foliae of chloritic and micaceous material. 

Quartz : The individuals are numerous, and markedly elongated and interlocked, frequently with 
irregular extinction. Inclusions of rutile occur. 

Chlorite and Sericite : The foliation of the rock is marked by numerous close-set parallel bands 
composed chiefly of chlorite or chloritized mica and sericitic matter, in elongated fibres. They are 
somewhat decomposed, with separation of yellow iron-oxide and dusty magnetite. 

Epidote : Is fairly common, granular to elongated in habit. 

Rutile : Occurs sparingly, granular in habit, or occasionally approaching the tj'pical geniculate 
form. 

Magnetite : A few small crystals occur. 



PLATE XVII. 




1. 





3. 



4. 



1. Serpentine fhom Stringburn, near Mount Hocken. Oi-dinary light. 

2. Hypersthene-diohite, Kawakau Gravels. Polarized light. 

3. Feldspar-porphtritb, Kawarau Gravels. Polarized light. 

4. Mica-gneiss, Kawarau Gravels. Ordinary light. 

All njannified :jO times. 



Bulletin A'o. o.} 



\To face p. 7* 



79 



Remarks. — The essential difference between this rock and its associate is its more arenaceous 
character, the upper schist being of a more argillaceous type. 

Analysis by Dr. Maclaurin. 



Silica (SiOj) 










6110 


Alumina (AI2O3) 










. 17-65 


Ferric oxide (FejOj) 










3-64 


Ferrous oxide (FeO) . . 










2-74 


Manganous oxide (MnO) 










0-22 


Lime (CaO) 










4-63 


Magnesia (MgO) 










0-25 


Chromic oxide (CrjO,) 












Titanium-oxide (Tit) 2) 










1-42 


Potassium -oxide (Kj^)) 










1-66 


Sodium-oxide (Na^O) 










4-38 


Carbonic anhydride (CUj) 










014 


Water, and loss in ignition 










1-50 



Total 



99-33 



5. Serpentine.— This rock composes the main mass of the dyke near the head of the Springburn, 
a branch of the Gentle Annie Creek. 

Macroscopic Examination. — S.g., 2-68. A massive dark-green serpentine rock, containing 
numerous small veiulets and aggregates of fibrous amphibole, calcite, and talc. 

Microscopic Exa.mination. — The rock is composed almost wholly of serpentine, sho-wing ffe- 
quently an irregular mesh -structure, indicating a derivation from olivine. A fair quantity of fine 
granular calcite is scattered through the rock, as well as some large irregular squares and skeletons 
of magnetite, and one or two cubes of pyrite. There are a few unaltered and partially altered cores of 
olivine, with strings of fibrous serpentine through them. 

The calcite has a good deal of dusty magnetite associated with it, and these constituents may be 
the alteration-products of ferro-magnesian constituents. 

Remarks. ^Judging from the uniform nature of the serpentine, and from the alteration-products 
present, the original rock was probably composed ver\' largely of olivine, with a subordinate quantity 
of enstatite or other pyroxene. 

The folio-wing analyses show the composition of the massive and fibrous of the serpentine : — 

Analyses by Dr. Maclaurin. 

Silica (SiOa) 
Alumina (AljOj) 
Ferric oxide (FejOj) 
Ferrous oxide (FeO) 
Manganous oxide (MnO) 
Lime (CaO) 
Magnesia (MgO) . . 
Chromic oxide (CrjOj) 
Titanium-oxide (TiOo) 
Pot£.ssium-oxide (KjO) 
Sodium- oxide (NajO) 
Carbonic- anhydride (CO 2) 
Water, and loss by ignition (HjO) 



Massive 


Fibrous 


Serpentine. 


Serpentine 


39-05 


51-90 


9-98 


2-83 


3-20 


3-72 


10-97 


4-17 


0-39 


0-57 


2-35 


9-00 


25-34 


23-42 


0-20 


0-10 


0-92 


0-11 


0-10 


0-10 


0-14 


005 


7-66 


4-52 



Totals 



100-30 



100-49 



80 



The subjoined analyses show the composition of the altered mica-schist at the contact -with the 
serpentine dyke, and of the unaltered mica-schist two yards from the dyke : — 



Silica (SiO,) 
Alumina (AI2O3) 
Ferric oxide (FcaO.,) 
Ferrous oxide (FeO) 
Manganous oxide (MnO) 
Lime (CaO) 
Magnesia (MgO) . . 
Chromic oxide (^203) 
Titanium-oxide (TiOa) 
Potassium-oxide (KoO) 
Sodium-oxide (NagO) 
Carbonic anhydride (CO, 



Analysis by Dr. Madaurin. 



Water, and loss by ignition (HgO) 



Totals . 



Unalterea 

Mica- schist. 

65-20 


Altered 

Mica schist 

60-82 


17-35 


20-07 


5-11 


4-97 


0-20 


0-14 


3-75 


1-79 


010 


012 


0-82 


92 


2-21 


0-56 


2-91 


8 07 


85 


0-57 


1-21 


1-30 



99-71 



99-33 



The most noticeable features disclosed by the analyses are the marked mcrease of the soda-alkali 
in the schist at the igneous contact, and the decrease of silica. The increase of the alkali must be due 
to migration from the basic magma, and local concentration along the contact. The other differences 
may be mostly due to variation in the composition of the original sediments in the two horizons from 
which the samples were collected. 



Detrital Igneous and Altered Rocks. 

5, Hypersthene-diorite. — This occurs as occasional rounded pebbles in the gravels of the 
Kawarau River. 

Macroscopic Examination. — S.g., 2-85. An aggregate of pink feldspar and pyroxene, with 
occasional dark veins. 

Microscopic Examination. — The rock is holocrystalline, composed almost entirely of plagioclase 
and hypersthene, the latter slightly altered. The structure is allotriomorphic. 

Plagioclase : Labradorite and andesine, in irregularly disposed plates, twinned on the albite law, 
with occasional Carlsbad and pericline twins, showing cross-hatching. It is full of inclusions, and 
somewhat clouded by calcite and sericite. 

Hypersthene : Occurs in irregular flakes, idiomorphic to the feldspar. Schiller-inclusions of dusty 
magnet'te occur commonly along the cleavage-planes. Occasional twins are present. The colour is 
pale when pure, but the mineral is largely coloured green by chloritization, and the formation of bastite 
pseudomorphs. Some iron-oxide has a'so separated out. 

Magnetite : Sharp-edged crystals are fairly common, and often large. 

Remarks. — The rock is a simple hypersthene-diorite, practically devoid of accessory minerals. 
One section shows a vein, evidently a contraction-crack filled by matter which has a porphyritic 
facies. The vein is sharply divided from the enclosing rock by a fringe of magnetite. The interior is 
composed of rounded crystals of plagioclase and hypersthene enclosed in a dark crypto -crystalline 
base. 



6. Feldspar-porphyrite. — Occurs as occasional pebbles in the Kawarau River gravels. 
Macroscopic Examination, — S.g., 2-79. A mass of porphyritic crystals of feldspar set in a 
dark fine-grained base, 



PLATE XVIII. 





1. BiOTiTE-GRANiTE, Kawarau Guavels. Poliirizt'd light. 

2. AuGiTE-HYPERSTHENE-DiOKiTE, Kawakau Gravels. Ordinary li;iht. 

3. AuGiTE-DiORiTE, Kawarau Gravels. Ordinary light. 

4. Hornblende-schist, Kawarau Gravels. Ordinary light. 

.\11 rnaKnified 30 times. 



Bulletin No. 5.j 



[To face p. 81. 



81 

MiCEOSCOPic Examination. — The rock consists of large crystals of plagioclase, with numerous 
smaller crystals of green hornblende, both highly decomposed, enclosed in a groundmass of pla^ioclase, 
hornblende, and magnetite. 

Plagioclase : Large crystals of labradorite, completely idiomorphic, with albite and Carlsbad 
twinning. They are crowded with needles of green hornblende, and grains of magnetite, and clouded 
with calcite and kaolin. 

Hornblende : Green hornblende is very prominent, in small, irregularly interlaced plates and fibres, 
highly decomposed, mth separation of magnetite and ferruginous and chloritic staining. 

Groundmass : This is quite subordinate. It consists of grains of magnetite, needles of feldspar and 
hornblende, and a Uttle interstitial quartz. 

Remarks. — The rock is a typical porphyrite, wholly crystalline. The separation of most of the 
hornblende appears to have taken place between the separation of the large feldspar.s and the solidifi- 
cation of the residual groundmass. The feldspar in particular is highly altered, and the nature of the 
alteration signifies more than simple weathering, being akin to that seen in andesites altered bv 
thermal solutions. 

8. Mica-gneiss. — Occurs as occasional boulders and pebbles in the gravels of tlie Kawarau 
River. 

Macroscopic Examination. — S.g., 2-81. A gneissic rock, consisting of alternate bands of quartz 
and green mica. Occasional fine quartz veins cross the grain of the rock. 

Microscopic Examination. — The rock consists essentially of a mosaic of quartz crystals, with 
some ragged green mica, typically in smaller proportion, and a little orthoelase. 

Quartz : Occurs in clear irregular crystals, crowded wth needles of apatite, and a little spheiie. 

Mica : A green variety, highly chloritized, with low birefringence. It occurs in bands of irregular 
or skeleton crystals. The bright-green colour suggests chrome-mica in places, but the low birefringence 
indicates that the mineral has been much altered. 

Feldspar : A few plates of orthoelase are present. 

Magnetite : This occurs in irregular grains and elongated threads, apparently filling contraction- 
cracks in the quartz. These and the needles of apatite and sphene show a common orientation. 

Apatite and sphene are present, the former in needles, the latter in grains and wedge-shaped crystals, 
included in and associated with the quartz. 

Remarks. — The gneissic banding is marked by the disposition of mica blades and apatite needles, 
and by the curiously elongated forms of magnetite. The last feature in particular seems to indicate 
that the gneissic structure was impressed immediately previous to the solidification of the rock. The 
alteration of the mica is probably to be referred to a cause acting about this period. 

9. Biotite-granite. — This rock occurs as occasional pebbles in the Kawarau gravels. 
Macroscopic Examination. — S.g., 2-67. A holocrj'stalline aggregate of quartz, feldspar, and 

brown mica. The rock encloses frequent basic fine-grained secretions up to 2 in. in diameter, in which 
ferro-magnesian minerals are more highly developed than elsewhere. 

Microscopic Examination. — An aggregate of clear and clouded plagioclase crystals, with biotite 
and some quartz. 

Plagioclase : Chiefly albite-oligoclase, in rectangular or elongated plates, with albite and Carlsbad 
twinning ; some microcline, wth characteri.stic cross-hatching ; a little orthoelase and micro-perthite. 
A Carlsbad twin sometimes encloses a core t\vinned on the albite law. The feldspars are slightly 
clouded with kaolin, and with fine sericite fibres lying r.long the cleavage-planes. 

Quartz : Is in clear, coarse, irregular crystals. 

Biotite : In square cleavage-flakes, brown, or occasionally green by chloritization. 

Hornblende : The brown variety is present in small quantity. 

Sphene : A few coarse grains occur. 

Magnetite : Occurs commonly, in coarse crystals associated with the biotite, and to some extent 
derived from it. 
6 — Cromwell. 



82 

Remarks. — The most noticeable features in this typical granite are the variety of structure of its 
feldspars, and the remarkable basic secretions, which have not been hitherto described in any granite 
in New Zealand. 

10. Augite-hypersthene-diorite. — Occurs as occasional pebbles in the Kawarau River 
gravels. 

Macroscopic Examination. — S.g., 2-78. A dense holocrystalline aggregate of feldspar and augite. 
The weathered surface is lighter owing to the decomposition of the feldspar. 

Microscopic Examination. — The rock is essentially composed of plagioclase and augite, the latter 
with a large development of magnetite, and some hypersthene. A small amount of biotite is also 
present. 

Plagioclase : Chiefly labradorite, in clear rectangular plates exhibiting fine albite twinning. 

Augite : In pale irregular or rounded crystals. The individuals have generally a green chloritic 
fringe, and a prominent development of secondary magnetite, in .strings surrounding and traversing 
them, often along the cleavage-lines. The extreme stage of alteration is seen in occasional cores of 
magnetite, with a green-brown fringe. 

Hypersthene : In pale crystals, rectangular or irregular, often enclosed within augite. Schiller- 
inclusions of magnetite are frequently seen. It is subordinate in quantity. 

Biotite : A few small flakes occur, associated with the augite. 

Apatite. : Is fairly common, in long needles with characteristic cross-fracture. 

Remarks. — There is considerable variety of ferro-magnesian minerals in this diorite. They are all 
idiomorphic to the feldspar, but the augite, which occurs in largest quantity, and appears to have been 
the last of the three to cry.stallize out, has generally an irregular outline, and was probably almost con- 
temporaneous with the feldspar. 

23. Augite-diorite. — Occurs as occasional pebbles in the Kawarau River gravels. 

Macroscopic Examination. — S.g., 2-87. A holocrystalline aggregate of feldspar, biotite, and 
augite, the latter largely developed and frequently iron-stained. There are occasionally more basic 
secretions, chiefly of augito. 

Microscopic Examination. — The rock consists essentially of fresh plagioclase and rather altered 
augite, neither mineral being uniformly idiomorphic to the other. 

Plagioclase : Andesine and labradorite, with conspicuous albite twinning. The crystals are some- 
times wrapped by augite, and sometimes the reverse order is seen. They are comparatively fresh. 

Augite : Generally in large, ragged, or irregular crystals, showing good cleavages. The corroded 
boundaries seem to be to some extent the effect of metaraorphic processes, the alteration-products of 
the augite being coarse and ragged magnetite in fringes and irregular growths around and within the 
augite, and brown oxidized matter. 

Biotite : Is present, but not in large amount, and may be in part an alteration-product of augite. 
It is sometimes largely replaced by magnetite. 

Sphene and apatite in their usual forms are constant, but not abundant accessories. 

Quartz : A little interstitial quartz is present, but rare. 

Magnetite : Large irregular patches are common, mostly resulting from the alteration of the augite 
and biotite. 

Remarks. — In this rock the augite appears to have commenced to crystallize prior to the feldspar, 
and continued to cr}'stallize to a later .stage. The augite has been strongly affected by dynamic pro- 
cesses, which have not left their mark on the feldspar. 

25. Hornblende-schist. — Fairly common as rounded pebbles in the Kawarau River 
gravels. 

Macroscopic Examination. — S.g., 2-84. A fine-grained schistose aggregate of hornblende. The 
rock is traversed by small quartz veins, and is frequently stained, greenish-yellow by chloritic or ser- 
pentinous products. 



PLATE XIX 




1. 




1. HOHNBLKNDE-CAMPTOJS'ITE, FROM TeRRACE NEAR BeNDIGO Goi.DFIELD. Orililiarv light. 

2. Mica-schist, Double Coxe, Eemarkabi.es. Ordinary light. 

3. Mica-schist, Bendigo Goldfield. Polarized light. 

All magnified 30 times. 



Bulletin Xu. 5.] 



[To face. p. 83. 



83 

Microscopic Examination. — An aggregate of fibrous green hornblende, the individuals markedly 
elongated in the direction of schistosity, with interstitial quartz. 

Hornhlende : The green fibrous variety, frequently patchj'-coloured or brown by alteration. The 
individuals are in medium-sized narrow rectangular plates, without distinct terniLaal boundaries. 

Quartz : Clear or clouded tine-grained quartz occupies the interspaces of the rock, and is quite 
subordinate in quantity. Associated vrith it is a considerable development of secondary calcite, derived 
from the hornblende 

Apatde : Occurs with the quartz in long thin needles. 

Sphene, iu rounded or wedge-shaped ciystals, is prominent in association with the hornblende. 

Remarks. — The foliation is crossed by fine strings of serpeutinous matter filling cracks. The 
schistosity, marked out by the arrangement of the hornblende, is particularly well developed. 

29. Hornblende-diorite. — Occurs as roimded pebbles and boulders in the Kawarau River 
gravels. It is rare. 

Macroscopic Examination. — S.g., 2-87. A massive coarse aggregate of hornblende and feldspar, 
with occasional segregations of hornblende, and with frequent chloritic staining. 

Microscopic Exa.mination. — The rock consists essentially of large corroded crystals of hornblende, 
and plagioclase crA'stals, the latter crowded with inclusions and decomposition-products. 

Hornblende : Brown, largely altered to green by chloritization, with separation of magnetite iu 
numerous small grains. The individuals are large and flaky, with occasional sharp boundaries, but more 
usually ragged and broken. 

Plagioclase : Chiefly andesine, in plates of var}'ing size, with irregular boundaries. They are 
clouded with sericitic matter. The twinning is rather obscure, but appears to be on the Carlsbad and 
albite law. Much calcite is also present as a decomposition-product. 

Auyite : Is present in small quantity, wrapped round and penetrated by green hornblende, which 
appears in places to be derived from the augite by uralitization. 

Quartz : Occurs interstitially. 

Sphene : A little is present in small grains. 

Magnetite : Occurs in small ( n'stals, but is rare. 

Re.marks. — The rock has the typical minerals of a hornblende-diorite, although augite appears 
originally to have been present in greater quantity. The large proportion of hornblende makes the 
rock a basic variety, tending towards an amphibolite. 

96. Hornblende-camptonite. — A rounded pebble of this rock was found in the morainic 
terrace below the Bendigo reefs. 

Macroscopic Examination. — S.g., 2.89. A brown rock, tine in grain, and somewhat decom- 
posed. It is crowded with small glistening hornblende needles, and has numerous small pores through- 
out. 

Microscopic Examination. — A mass of long needles of brown hornblende, and smaller needles 
and granules of augite, imbedded in irregular plates of plagioclase. 

Hornblende, the most prominent constituent, is bro\\ii, in long rectangular needles or sheaves of 
needles, disposed in all directioiis. The individuals are somewhat decomposed, with retention of colour, 
but often with loss of pleochroism, as a result of iron-staining. There is a second generation of much 
smaller needles. 

Augite : Pale brow^n, is shorter and stumpier iu habit than the hornblende, and much less common. 
Some of the cross-sections of augite show diagonal twinning. 

Pla/jiodase : Occurs as shapeless plates of twinned labradorite, in which are imbedded and in- 
cluded the other constituents. The individuals are much clouded by decomposition. 

Apatite . Occurs as large needles with characteristic cross-fracture, penetrating the feldspar. 

Magnetite : Is very common in small and medium-sized grains. 

Remarks. — The rock is holociystalliue, no glassy base being recognisable. It has the texture 
of a dyke rock, and shows the peculiar feature of many lamprophyres — i.e., two generations of the ferro- 




84 

magnesiau constituents. The feldspar is not porphyritic, but was evidently tlie last constituent to 
separate out, which suggests that the residue after the separation of the bisilicates, had a composition 
approximating that of labradorite. The specimen has a fine- vesicular structure. The vesicles, which 
are unoccupied by secondary products, are probably original steam-pores. 

101. Pink Quartz-schist. — This rock occurs in small rounded pebbles and in large 
masses in the morainic terrace drifts of Cromwell basin, and in the terrace gravels near the mouth 
of Soho Creek. It occurs in situ on the higher flanks of Black Peak on the south side of Matukituki 
Valley. 

Macroscopic Examination. — Sp. gr., 2-66. A fine-grained rock consisting of narrow bands of 
grey and pink quartz, the latter imparting a fine rose or pink colour. Slightly schistose. 

Microscopic Examination. — When in thiji slice, is seen to consist essentially of grey and red 
granules of quartz. 

Quartz : The grains are arranged in distinct bands, and are elongated in the direction of the foliation. 
Contains fluid-cavities. 

Rutile : This is present, but not common. 

Magnetite : Present in small grains. 
• Mica : A little grey sericitic mica is present. 

Remarks. — The pebble of red micaceous quartz-schist from the Clutha gravels, described iu Bulletin 
No. 2, page 42, from its external resemblance was supposed to be the same as the red quartz schist 
which occurs in large masses in Clyde moraine and on the higher flanks of Leaning Eock, facing Dtmstan 
Gorge. Examination this year has, however, shown that this red micaceous quartz-schist is rare, and 
occurs only in small pebbles ; while the pink quartz-schist occurs in large masses. The analysis quoted 

caceous quartz-schist is that of the pink quartz-schist, 

Analysis by Dr. Madaurin. 

89-86 
2-71 
0-40 
2-66 
1-02 



in Bulletin No. 2, page 43, as that of the red m 
and is as follows : — 



Silica (SiOa) 
A-lumina (AI2O3) 
Ferric oxide (FcjOa) 
Ferrous oxide (Fc-0) . . 
Manganoas oxide (MnO) 
Chromic oxide (CrjOy) 
Lime (CaO) . . 
Magnesia (MgO) 
Titanium- oxide (TiOj) 
Potassium- oxide (KgO) 
Sodium-oxide (NagO) 
Sulphuric anhydride (SO 3 
Carbon -dioxide (CO 2) 
Water lost below 100° C. 
Water lost above 100° C. 



010 

0-96 
0-78 
0-26 
0-56 
013 

005 
0-22 

99-71 



Detrital Sedimentary Rocks. 

11. Greywacke. — ^Frequent pebbles and boulders in the Kawarau River gravels. 

Macroscopic Examination. — S.g., 2-52. A greyish-green rock, tough, fine-grained, and siliceous. 
It is traversed by fine quartz veins, along which serpentinization is more or less marked. 

Microscopic Examination. — An even-grained mosaic of clear angular quartz, and dark ferro- 
magnesian matter, in about equal quantity. 

Quartz : The fragments are small, rounded, and sharp-edged, showing no signs of crystalline 
enlargement. They contain liquid inclusions and dust. 



PLATE XX. 




1. 





1. Schistose Greywacke, from Flanks of Carrick Range. Ordinary light. 

2. Greywacke, Kawarau Gravels. Ordinary light. 

3. Altered Greywacke, Double Cone. Ordinary light. 

4. Greywacke, Kawarau Gravels. Ordinary light. 

All magnified .30 times. 



Bulletin No. -5.] 



[To face p. 85. 



85 

The remainder of the rock consists of dark-green cloudy matter, the result of alteration, to chlorite 
and other products, of the original ferro-magnesian constituents. A few fragments of biotite and tureen 
hornblende can be recognised, also a Uttle kaolinized feldspar. 

11a Greywacke. — Occurs very commonly as romided boulders in the gravels of the Kawarau 
River. 

Macroscopic Examination. — S.g.,'"2-68. A dark bluish-grey rock, much finer in texture than the 
above. It is highly siliceous, and contains much dark mica in fine scales. It has a tendency to a fine- 
foliated structure. 

Microscopic Examination. — A ver)' dense fine-grained aggregate. The quartz grains are very 
small, and not distinguishable in great quantity. Mica and hornblende are present, but the bulk of the 
rock consists of very dark irresolvable matter, which the green colour of the hand-specimen shows 
to contain a considerable amount of serpentinous and chloritic products. There are very distinct 
appearances of a parallel or banded arrangement of particles, and the rock thus approaches verj' near 
to a phyllite. The silicification and cementation of the rock have rendered it more homogeneous, and 
destroyed the typical coarse-grained structure seen in the other grex-wackes. 

12. Greywacke. — Very frequent as boulders and pebbles in the Kawarau River gravels. 

Macroscopic Examination. — S.g., 2-63. A dense fine-grained buff- or ])cppcr-coloured rock, 
studded with fine silvery micaceous scales, and coarser blebs of red iron-oxide and ^reen serpentinous 
matter. 

Microscopic Examination. — A highly siliceoua rock, coarser in grain than the other grey- 
wackes. 

Quartz : The small fragments are char and angular, the larger are clouded and rounded, which 
probably indicates enlargement of pre-existing grains by silicificatiou. 

Feldspar : A few small clouded rectangles occur. 

Mica : There appears to have been a considerable quantity of brown mica, and probably hornblende, 
present, represented now by the considerable quantity' of dense cloudy alteration-products, patches of 
iron-peroxide, and of ragged magnetite. 

36. Greywacke. — Occurs commonly as roimded included pebbles in boulders of Te Anau 
conglomerate in the Kawarau River gravels. 

Macroscopic Examination. — S.g., 270. A light-green rock, tough and fine-grained. It is 
very similar to No. 11, but lighter in colour. 

Microscopic Examination. — An aggregate of fairly coarse quartz and ferro-magnesian minerals, 
the latter largely decomposed. 

Quartz : In irregular grains of various sizes, containing inclusions of dust and rutile needles. The 
occasional irregular extinction and the elongation or banding of the lines of fine inclusions seem to point 
to derivation from a schist. 

The remainder of the rock is chiefly bro^vTl mica, coarser and less altered than in the other grey- 
wackes. The first stage of alteration is chloritization, followed by the separation of iron-oxide. A 
little plagioclase, highly decomposed with the formation of calcite, is present. A little rutile and mag- 
netite are present in small grains. 

37. Sandstone. — Occurs as occasional pebbles in the gravels of the Kawarau River. 
Macroscopic Examination.— S.g., 2-72. A Ught-grey rock of medium grain. It is highly siliceous 

and fairly micaceous. 

Microscopic Examination. — A fine mosaic of coarse angular quartz, decomposing mica, and 
some plagioclase. 

Quartz : In coarse grains, with clear but somewhat roimded edges, and inclusions of liquid and 
materials. The rounding of the grains appears to be rather the result of attrition of the original grains, 
than of crystalline growth. 



86 

Mica : A brown variety, in moderate quantity, largely bleached, and also chloritized, with the 
separation of grains and enveloping strings of magnetite. 

Feldspar : Chiefly plagioclase ; is common in plates, clouded with calcite and kaolin. 

Magnetite : Is present as occasional grains. 

Remarks. — The rock has the constituent minerals of a granite, from which, or similar rock, it haa 
probably been derived. 



H7 



INDEX. 



" Acheron," H.M.S. 
Acknowledgements . . 
Actinolite . . 

Adams's Gully, (Sold in scliist-wash 
Age of Bendigo and Carrick lodes 
„ Central Otago i)eneplain 
,, Kakanui Series 
„ Maniototo Series 
.\lbite-oligoclase 
Alluvial gold 

{See also Table of Contents, Chapter iv.) 
Alluvial wash in Rise and Shine Creek 
Alpine vegetation 
Alta lode . . 
Altered grevwacke . . 
Amjihibole 
Analyses . . . . 68, 6ft, 70, 71. 72 

{See also Assays.) 
Anderson's Creek, VVaikerikeri, Schist and 

cene beds at 
Anderson's lode 
Andesine 
Antimonite 
Antimony . . 

,, .Analysis of 
,, Buchan's lodes 
,, Horn's lode 
Apatite 

Area dealt with in bulletin 
Argillaceous mica-schist 
.Arrow Flat 

,, Floor of 

Arrow Valley 

,, Fluvio-glacial drift in 

Arsenical pyrite 

Artesian water in Central Otago 
.^bestos 
Assays 

{See also Analyses.) 
.Auckland I.sthmus, Volcanic region of 
-Augite 

,, -diorite 

,, .hypersthene-diorite 
.Aurora lode 



Page 
3 

3 
29 
46 
63 

7 

30 ! 
28 i 
81 , 
40 



•2 



no 
78 
(>8,79 
73. 77. 79, 84 

Plio. 

9, 10 

54 

80, 82, 83 

67 

29. t)3. 66, 67 

68 

67 

«7 

81,82,83 

1 

.■)7 

21 

21 

20 

21 

57 

73 

29, 68 

4 1 . 6.">. 66 

27 
82,83 
82 
82 
53 



B. 

Bannockburn Co.ilticld 

{See also Coal.) 
Bannockburn CoalKeld, Faulting at 

„ Fault, Schist and Pliocene beds 

along the 
„ Gold-bearing gravels at 

,, Gravel terraces at 

,, Lake- beds at 

„ Prospecting of drifts at 

,, section of lacu.strine series 

„ section of lacustrine series. Sue 

cession of beds of 
,, section of lacustrine series, Thick 

ness of 
,, Survey District 

,, Township of 

Valley 



14 

10 
,42 
2(» 
17 
41 
32 

32 

33 
J 
1 

20 



50. 



29,81, 



Barewood plateau of erosion . . 
Basalt boulders In Clutha River gravels, Cromwell 
basin . . . . . . . . 15, 18 

Ba-^e-levcl plain of erosion of Central and Eastern 

Otago 

Ba.stion Channel 

Rock 
Battery Creek 
Bee lode 
., Spur 
Bendigo ( 'reck 
Bendigo gold-bearing lodes 
., veins 

Bendigo (Joldtield . . 

{See also Table of Contents, Cliajiter iv.) 
Bendigo .Mine 
Bendigo and Carrick lodes, (Jencsis of . . 

{See also Table of Contents, Chapter iv.) 
Biotite 

-granite 
Black Horse lode 

Black sand in gold drifts. Source of . . 
Block mountains 

„ Systematic investigation of 

,, Systematic investigation of : 

Scheme frtr. by I'rofessor W. 
.M. Davis . . ■ 
Blowing-down .system of sluicing 
.Scope of system 
.Actual working 
Blue Spur Claim near Lawrence, Section of work- 
ing-face of. Fig. 3 . . 
Boundary ( 'reek 
Bnidford's lode 

Breccia : Bouldsrs of, in Clutha River gravels 
Brewery Creek, river-gravels in 
Brown coal in Oamaru Series 

in lacustrine beds, Roaring Meg Coal- 
basin . . 
,, in lacustrine beds, Gibbston ooal- basin 

Buchan's antimony lodes 



c. 



Calcite 29, 75, 76. 77, 79, 80 

Caledonia lode 
Cardrona Codl-mine 
Saddle 
,, Valley 

Carrick (ioldfield 

{See also Table of Contents, Chapter iv.) 
Carrick gold-bearing lodes 

{See also Table of Contents, Chapter iv.) 
Carrick gold-bearing veins 

., and Bendigo lodes. Genesis of . . 
{See (dso Table of Contents, ('ha|)tcr iv.) 
Carrick and Pisa liorsts. Genesis of . . 

,, Range . . 9 

,, ., Antimony-ore on 

,, ,, Crumbling schist wash on 

„ „ Fault at foot of 

„ ,, Summit of 

Carricktown lodes 

(See also Table of Contents, Chapter iv.) 



P««e 



10,34 

2,9 

15 

15 

51,52 

53 

53 

55,56 

48,49 

29 

49 

4ft 
63 

82, 85 
81 
t)2 
25 
8.9 
13 



13 
47 
47 
47 

10 
12.21 
55 
15 
14 

19 

:<o 

67 



83, 86 
60.63 
72 
1ft 
20 
57 



2, 48, .58 

29, 41 
63 

12 
11,16, .57 
66 
46 
11 
2,11 
61 



81, 



88 



Page 

Celmisias . . . . . . . . . . 23 

Cement stones, or " Chinamen " . . . . 33 

Central Otago base-level of erosion . . . . 6 

,. Geology of . . . . . . 3 

,, peneplain . . . . . . 6 

„ „ Age of . . . . 7 

,, ,, Origin of . . . . 8 

Cervantite . . . . . . . . . . 67 

Chinatown, Depth of shaft of loal-inine at . . 14 

Chlorite . . . . . . . . 2"). 75. 76, 77, 78 

„ -schist .. .. .. .. 3, 12, 34 

„ ,, of Kakanui Series . . . . 30 

,, ,, of Maniototo Series . . . . 24, 25 

„ ,, Origin of . . . . . . 3, 25 

,, ,, Thickness of . . . . . . 25 

Chloritic quartz-schist . . . . . . 76 

mica-schist . . . . . . 28, 29 

Chloritoid schist of Kakanui Series . . . . 30 

,, mica-schist of Maniototo Series . . 25 

Cinnabar . . . . . . . . . . 63 

Clays in lake-beds at Bannockbum . . . . 17 

,, Marine . . . . . . . . 8 

" Cleat " or series of cleavage-planes in coal of 

Excelsior Mine . . . . . . . . 70 

Clutha Flat, Depth of coal measures in the . . 14 

,, Vegetation on . . . . . . 23 

Climate . . . . . . . . . . 23 

Clutha glacier . . . . . . 19, 20, 45 

,, -Kawaraii glacier . . . . . . 45 

„ Oorge . . . . . . . . 7 

River .. .. . . 14, 15, 18, 19, 22 

„ Flow of . . .... 22 

„ gravels . . . . 15, 18, 20 

,, ,, sands . . . . . . 18 

Clyde moraine . . . . . . 15, 19, 21, 45 

,. Basalt and jiink ([uartzite on top of 34 

Coal ' . . . . . . . . . . 69 

(See also Table of Contents, Chapter iv.) 

Coal, Analysis of . . . . .. 69, 70, 71, 72, 73 

,, brown, in Oamaru Series . . . . 8 

Coal-measures on the Clutha Flat, Depth of . . 14 
„ at Roaring Meg and Gibbston, In- 
folding of r. . . . . 25 

Coastal plain . . . . . . . . 6 

Colleen Bawn lode . . . . . . . . 61 

Concentration in river-bed gravels. Some prin- 
ciples of . . . . . . . . . . 36 

{See also Table of Contents, Chapter iv.) 

Coneburn . . . . . . . . . . 12 

Conglomerates . . . . . . . . 8, 30 

Conglomerate boulders in Clutha River gravels . . 15 

Coralline limestones . . . . . . . . 8 

CVomwell basin . . . . 1, 3, 7, 13, 20, 21, 31, 33 

„ Building and filling-up of . . 18 

„ Depth of .... . . 14 

„ Destruction and construction of, 

by Clutha and Kawarau Rivers 18 

Floor of . . . . 14, 15, 17 

„ History of . . . . . . 17 

Lignite in . . . . . . 3, 69 

„ Origin of . . . . . . 16 

„ Outlet of . . . . 14, 15, 18 

,, Subsidence of . . . . 17, 18 

,, Fresh-water beds in . . . . 3 

Cromwell Flat . . . . .. 1, 12, 42, 45, 46 

,, Artesian water in . . . . 75 

„ Drifting sands on . . . . 35 

Cromwell glacier . . . . . . . . 20- 

,, (iorge . . . . . . . . 20 

„ lode^ . . . . . . . . 50 

„ Reservoir terrace . . . . . . 14, 33 

„ section of the lacustrine series 31 
„ section of the lacustrine series. Succes- 
sion of beds of . . . . . . 32 

„ Survey District . . . . . . 1 

„ terraces. Vegetation on . . . . '23 

„ Town of . . . . . . . , 1 









Page 


Cromwell, Town of, Fluvio-glacial drifts under the 46 


Cross-lodes 






49 


Cross-lode 






49 


Crown Survey District 






1 


,, terrace 






21 


,, and Cross lode 






58 


Crumbling schist wash 






46 


Crystalline rocks 






3 


of the 


Grampian Mountain."! in 


Scotland . . 


. 


3 



D. 

Davis, Professor W. M. 

,, „ Scheme for the systematic 

investigation of block 

mountains 

Deformed lake-basins . . . . 

,, Roaring Meg coal-basin 

,, (iibbston coal-basin 

,, lake-basins, Origin of 

Descent and ascent of gold in travelling drift 

Desert plains of Australia 

Detrital igneoiis and altered rocks 

(See also Table of Contents, Chapter v.) 
Detrital sedimentary rocks 
Devonshire alluvial workings, Fault-fracture ex 

posed at . . 
Diorite 

Disposition of strata of Maniototo Series 
Distribution of Kakanui Series 

„ Maniototo Series 

Doolan's Creek 

„ Coal in 

,, Flow of 

Double Cone, Remarkables 
Drift-travel, Rate of 
Drifts, Fluviatile 
,, Glacial 
,, Gold-bearing 
Drybread, Fault-fracture exjiosed in alluvial work 

ings at . . 
Dunstan divide 
,, Gorge 

,, ,, Terrace at ujiper end of the 

,, Mountains 

,, ,, Disposition of schists on 

„ „ Fault-fracture on eastern side 

of 
„ ,, Summit of 

,, peneplain . . 



E. 



12, 



7, 



10. 



13 
19 
19 
19 
20 
39 
8 
80 

84 

9 

•34 

25 

30 

24 

19, 22 
71, 72 

22 

11 

39 

3, 14 

3, 14 

3 

9 
57 

20, 21 
14, 18 
12, 16 

9 

9 

2, 9 

12 



East-and-west lodes 


50 


((SeT also Table of Contents, Chapter iv.) 




Economic geology . . 


36 


,, minerals of Kakanui Series 


31 


,, „ Maniototo Series 


29 


Elizabeth lode 


61 


Enstatite . . 


79 


Epidote . . . . . . . . 2, 75, 76, 77, 


78 


Epidotized chlorite-schist 


75 


Eruptive rocks of Kakanui Series 


31 


,, Maniototo Series 


28 


Excelsior Coal-mine at Bannockbum . . . . 18 


69 



F. 



False Uottom 

„ Power to arrest gold 

Farms, Irrigation 



37 

40 

1 



89 



Page 

Fault at foot of Carrick Range T • ■ • • ^ ^ 
:•' ,, -fracture on eastern side of Dxinstan Range y .:■ 9 
Feldspar .. .. .. 78,80,81,82,83,84,86,86 

,, -porphyrite . . . . . . 80 

Finlayson, Mr. A. Moncrieff, M.S.C. 3 

Fireclay . . . . . . . . 32 

Fissile shales . . . . . . . . 19 

Five-mile Stream, Native silver in . . . . 66 

Fluviatile debris in Kawarau moraine . . . . 33 

Fluviatile drifts ..f, .. .. 3,14,16,45 

„ ,, forming terraces . . . . 42 

„ gravels . . . . . . . . 34 

Fluvio-glacial deposits and moraines . . . . 14 

drifts . . . . 34, 46 

„ „ facing Arrowtown . . 21 

„ gravels . . . . 34 , 

Foliation of Maniototo Series . . . . 26 

Forbes, Dr. Charles . . . . . . 3 

Fraser River, Gravels of . . . . . . 20 

Fresh-water beds in Cromwell basin . . . . 3 

„ deposits . . . . . . 7, 16 

„ sediments . . . . 15, 16, 17 

Depth of .. .. ,• 17 

,, shells in lake-beds, Bannockbum ..-_(' , -^11 



G. 

Gajvie Range . . . . . . . . 11 

General description of district .. .. 1 

,, geological features . . . . . . 3 

,, geology . . . . . . . . 24 

,, information . . . . . . 1 

Crenesis of Bendigo and ( 'arrirk lodes . . 63 

(See also Table of Contents, Chapter iv.) 
Genesis of gold in Rise and Shine impregnated 

shear zone . , . . . . . . 57 

Genesis of Pisa and Carrick horsts . . 12 

Gentle Annie . . . . . . 19 

Geological literature . . . . . . 3 : 

Gibbston coal -basin . . . . . . . . 19 I 

,, ,, -mine . . . . . . 71 ! 

,, lacustrine coal-measures . . 20 

Flat .. .. .. 21 

Saddle . . . . . . . . 19 

Glaciation . . . . . . . . 12, 15 

Glacial drifts . . . . . . 3, 13, 14 

,, erosion . . . . 21 

Glaciers, Pleistocene advance of the . . 15 

Glacier-debris . . . . 33 

,, -detritus . . . . . . 3 

,, -gravels. Gold in . . . . . . 44 

CHycimerig . . 34 

Gold, Concentration of, in river-beds . . . . 37 

,, Descent and arrest of, in travelling drift . . 39 , 

,, Genesis of, in Rise and Shine impregnated ! 

shear zone . . „. .,. . . 57 | 

„ in bed of Roaring Meg . . . . 66 ' 

,, Origin of, in quartz drifts and terrace-gravels 42 

Gold-bearing drifts in Central Otago . . . . 3 

„ gravels at Bannockbum 35 ' 

,, gravels and glacier-detritus . . 3 

„ lodes . . . . . . . . 48 

(See uUo Table of Contents, Chapter ir. ) 

Gold-bearing strata at Blue Spur Claim . . 10 

,, veins at Bendigo and Carrick Range 29 

wash . . . . . . . . 38 

Gold- and scheelite-bearing ore . . . . 56 

Gtold-wash in Kawarau and Dunstan Gorges . . 38 

Golden (iate lode . . . . . . . . 62 | 

Golden Point, Gold-wash at . . . . . . 39 

Graben .^ „. . . 7 [ 

Grampian Moimtaina in^J^Scotland, Crystalline [ 

rocks of ... . . . . . . 3 I 

Granite . . . . . . . . 34, 82 

Granular chlorite-schist . . . . . . 77 I 

7— Cromwell. 









Page 






.31 


,65,68 
3,34 
37 
20 
34 
8 
34 


.'. 21, 


30, 


34, 


84, 85 



' Graphite 
Gravels 

Gravel drift or wash 
Gravel terraces at Bannockbum 
Green brecciasj 
Greensands 

Greyish-white crystalline limestone 
Greywacke 

,, in Cliitha gravels, Cromwell basin 14, 15, 18, 

21, 34 

,, in fluvio-glacial drift facing Arrowtown 21 

Grits . . . . . . . . . . 8 

Gritstone boulders in Clutha River gi-avels . . 15 



H. 



Hawea waterehed 








22 


Hawkdun Range 








12 


,, Marine shells at foot of 








7 


Hawsbum lode 








64 


,, Graphite on hanging- wall of 








68 


Hector's, Sir James, work in Central Otago 








4 


Henderson's lode 








66 


High-level flood-plain 






33, 


34 


,, gravels 






33, 


34 


History of Ci-omwell basin 








17 


Hit or Miss lode 








53 


Horn, Mi-. J., Chairman of Vincent County Council 




3 


Hornblende . . . . • • i 


81 


82, 


83, 


85 


,, -camptonite 








83 


,, -diorite . . 








83 


„ -schist . . 








82 


Horn's lode 








C7 


Hutton, Captain 








20 


Hydrothermal action 








57 


Hypersthene 




!80 


,81 


82 


,. -diorite . . 








80 



Ice erosion 

Ice-sculptured hill in Kawai'au Gorge 

Ida Valley, Artesian water in 

,, basin 

fault 

,, ,, Stratification of schiste and 

Pliocene beds 
Igneous dyke on Carrick Range 
Immature rei>lacement lodes 
Iron-oxide 
Iron-i)eroxide 
Irrigation farms 



John Bull lode 

,, quartz veins 



K. 

Kaikouia fault 
Kakanui Series 

{See also Table of Contents, Chapter iii 
Kalahari Desert 
Kaolin 

Kaolinised feldspar . . 
Kawarau glacier 

,, Gorge 

,, „ Fluvio-glacial deposits at lower 

end of 



12 
21 

74, 75 

7, 16 

10 

10 
29 
63 
85 
85 
1 



62 

65 







13 




28, 


30 
8 


78, 


81, 


86 

85 


18, 


21, 


45 


. 7, 


11, 


21 



45 



90 









Page 


KawardU 


Gorge, Gold- wash in 




-.37.38,45 




gravels 




2(1 




moraine 




18, 21, 33, 45 




River 




..14,18.22 




„ Flow of 




22 




,, Coal-outcrops on 


banks 


69 




Survey District 




1 


Kohinoor lode 




62 



Labradorite . . . . . . 80, 81, 82, 83 

Lacustrine .seiies . . . . . . . . 3, 31, 73 

,. ,, Bamiockburn section . . 32 
,, ,, Succession of beds of Bannock- 
burn section . . ... 32 

„ „ Depth of, Bannockburn section 33 

,, ,, Depth of, Cromwell section . . 31 
„ ,, Succession of beds of Cromwell 

section . . . . . . 32 

beds . . . . 4, 9, 16, 18, 19, 74 

„ „ at Chinese Camp, Cromwell . . 31, 32 

„ „ in CYomwell basin . . 14, 15, 16. 18, 21 

,, „ in Roaring Meg coal-basin . . 19, 71 

„ „ at Waikerikeri . . . . 10 

„ deposits in Cromwell Flat . . . . 12, 17 

„ sediments in deformed lake-basins . . 20 

„ „ Gibbston coal-basin . . 20 

Lake Alta . . . . . . . . . . 21 

„ Wakatipu . . . . . . . . 22 

,, ,, High-level gravels on eastern side 

of .. .. .. 33 

Lakes and mountain-tarns . . . . . . 21 

Lake-basins . . . . . .4, 7, 17, 19, 20. 73 

„ Existence of artesian water in . . 73 

Lake-beds in Cromwell basin . . . . . . 17 

Land, Surface of . . . . . . . . 1 

Leads at Quartz Reef Point . . . . . . 43 

Lignite .. .. .. .. 3,17,32,69-73 

Lignitic series . . . . . . . . 14, 31 

Limestone, Crystalline . . . . . . 34 

Limestones, Coralline . . . . . . 8 

Lindsay, Dr. W. Lauder . . . . . . 3 

Literature . . . . . . . . . . 3, 4 

Little, Mr. J., Mayor of Cromwell . . . . 3 

Lodes, {See Table of Contents, Chapter iv.) 

Lodes in basin of Roaring Meg . . . . 66 

Henderson's lode . . . . . . 66 

Roaring Meg veins . . . . . . 66 

Lowburn, Native silver in . . . . . . 66 

Low-level adit, Bendigo . . . . . . 55 

Lucknow lode . . . . . . . . 54 



Macdonald, ilr. A. Gordon, B.E. . . , . 3 

Magnetite . . 25, 75, 76, 78, 79, 80, 81, 82, 83, 84, 85, 86 

Maniototo basin . . . . . . . . 7 

„ Series . . . . . . . . 24 

{See also Table of Contents, Chapter iii.) 

Manuherikia basin . . . . . . . . 7, 13, 16 

„ „ Artesian water in . . . . 74, 75 

„ „ Fluvio - morainic matter in 

lower end of . . . . 45 

„ ,, Lacustrine beds of . . . . 4, 9, 16 

„ River . . . . . . . . 16 

" Maori bottom " . . . . . . 18, 33, 42 

Maps, Topographj^ on, &c. . . . . . . 2 

Marine beds between Taranaki and Ruahine 

Range 
Marine clajs 
„ deposits 

shells, Beds of 
' • strata of Eocene age . . 



Marquis of Lome lode 
Matakauri . . 
Metamorphic rocks . . 

(See also Table of Contents, Chapter v.) 
Metaraorphism of Maniototo schists 
McDouall, Mr. Philip H. 
McDougall's coal-mine 
Mica . . . . . . 76, 77, 81, 

„ -gneiss 

„ -schist . . 3, 7, 12, 14, 28, 29, 

{See also Kakanui and Maniototo Series.) 
Mica-schist, Castellated piles or tors of 
of Kakanui Series 
of Maniototo Series 
Origin of 

in Roaring Meg coal- basin 
Thickness of . . 
Micaceous quartz -schist 
„ shale 

„ slate 

Microcline . . 
ilicro-perthite 
iliddle lode, Bendigo 
ilinas Prietas gold- and silver-bearing 
Mineralised shear zones 
Miocene strata 
Mitre or Moonlight Creek 
Modified glacier drift 
Morainic debris in Cromwell basin 
„ drift in Cromwell basin 
,, matter 

„ Gold in 
Motutapu VaUej' 
Mount Colin 

Crup.chan 
Difficulty 

,, Veins of antimony on 

Dottrel 1 . . .. " 

Geikie 
Gilray 
Hocken 

Ida, Marine shells at foot of 

Malcolm 

Pisa 

Ramsay 

St. Mary beds 

Mountains, Composition of 

Mountain plateaux. Height of 

,, ranges 

„ ,, Carrick Range . . 9, 

„ ,, Dunstan Mountains . . 9, 

„ „ Pisa Range . . 

,, ,. Remarkable Mountains 

,, tarns 

iludstones . . 

Mullocky lodes 

Muscovite . . 



N. 



Xew Caledonia lode . . 

,, Find lode 

„ Royal Standard No. 1 lode 
No. 2 lode 
Nevis Bluff 

„ River 

„ „ Flow of . . 

„ „ Gravel terraces at mouth^of 
North lode . . 



Page 

62 

23 

3, 75 

25 

3 

19 

84, 85, 86 

81 

34, 78, 80 

12 

30 

24 

3, 25 

19 

3, 25 

25, 49, 76 

31 

65 

81 

81 

50 

57 

57 

15 

66 

34 

19 

15 

33 

44 

20 

66 

11 

11 

68 

11 

11 

66 

23 

7 

23 

11 

11 

28 

3 

1 

2, 9 

11, 16, 57 

10, 12, 16 

9, 11, 16 

11 

21 

28, 30 

66 

76, 77 



60 
59 
58 
58 
11 
2-2 
22 
33 
50 



0. 



Oamaru Series 

Old Heart of Oak lode 

OUgodase . . 



7, 8 
75 



91 



Olivine 

Orewa, Section of portion of the sea-cliff near 

Origin of Central Otago peneplain 

„ Croinwell basin 

„ deformed lake- basins 

„ Maniototo schists 

„ minerals in Bendigo and Carrick lodes 

„ peneplains 

„ chlorite- and mica-schists 
Orthoclase . . 
Ostrm, Shells of 



Pase 




Pag» 


79 


Quartz, Veins of, in Kakanui Series 


31 


•27 


„ -chlorite-scliist (with eiiidote) . . 


75 


8 


„ -schist 


75 


15 


„ Reef Point, Alluvial leads at . . 


42 


•20 


,, ,, Creek . . 


43 


•25 


Quartzose antimonite 


07 


s 03 


,, mica-schist 


. 35, 49 


6 


,, sands in (Jibbston coal-basin 


20 


3 


,, sands and grits in lake-beds at Crom 




81 


well 


17 


34 


Queensbury Range, Coal on . . 


71 



P. 

Palaeozoic mica-schist 

,, shore-line 

Passarge's postulate 
Pasture 

Pay-ore in Bendigo and Carrick lodes. Position of 
Pay-wash . . 

Position of 
Peat bogs, Growth of 
Peneplains, Origin of 
Petrography 
Phyllite .. .. .. .. ..57, 

Physiography 

Pink quartzite in Clutha River gravels 
,, quartz-schist . . . . . . . . 15, 

Pipeclay Gully : Gold in crumbling schist wash 
,, lodes 

(See also Tabic of Contents, Cha|)ter iv.) 
Pisa and Carrick horsU. (Jenesis of 
fault . . 

,, Schists and Pliocene beds along the . . 
Range . . . . . . . . 9, 

Quartz veins on Hanks of . . 
,, Native silver in streams . . 
,, Summit of 
Plagioclase . . . . 75, 70, 77. 78, 80, 81, 82, 83, 

Plankburn 

,, basin. Coal in 

Plateaux. Mountain : Height of 
Pleistocene series 

(See also Table of Contents, Chapter iii.) 
Pleistocene detritus 
,, gravels . . 

,, terrace gravels 

Pliocene (lacustrine series) 
Bannockbum section 
Cromwell section 
Pliocene beds 

,, ., at Anderson's Creek 

,, ,, Stratification of, at Ida Valley, 

Pisa and Bannockbum faults . . 
,. ,, Tucking-in of . . 

„ gravels 
,, quartz drifts 
„ strata 
,, lacustrine beda .. .. ..11, 

Powell's cycle of iluviatile erosion 

Previous geological work 

Pyrite .. .. .. .. ..56, 

P3rro.\ene . . 
Puketoi Range 



R. 



J 2 


Rasgidy Ridge 


9 


3 


Rainfafl .. 


2 


(i 


Ranges, table-topped 


6 


2 


Recent deposits 


35 


04 


,,' detritus 


74 


43 


Red micaceous quartz-schist 


84 


37 


" Reef bottom " 


37 


17 


Relation of Kakanui Series to overlying format ion 


30 





,, „ underlying formation 


30 


75 


„ Maniototo Series to underlying forma- 




, 05, 08 


tion . . 


27 


3 


Remarkable Mountains 


11 


18. 34 


Re-sorted fluvio-glacial drift . . 


45 


19.84 


Rickard, Mr. T. A. . . 


(i3 


4(> 


Rift-valley at foot of Kaimanawa Mountains 


(> 


02 


., -valleys 


7 




Rise and Shine Creek 


57 


12 


Gully 


57 


11. 12 


impregnated shear zone 


49, 56 


1(1 


,, iiiiprcimatcd shear zone. (Icncsis 




11. 10 


of gold in . . 


57 


0(i 


Rivers 


22 


00 


River-bed gi-avels and sands 


46 


1. II 


Some principles of concentra- 




85, Hti 


tion in . . 


36 


19. 22 


(Sec also Table of Contents, Cha]>ter iv.) 




71 


River-bed gravels. Terraces formed of the. near 




I 


( 'romwell Bridge 


30 


33 


River-drift . . 


45 




River erosion. Progress of . . 


36 


74 


Roaring Meg 


19. 22 


33 


Flow of 


22 


50 


„ Suggestions for utilising water of . . 


22 


31 


,, coal 


71 


32 


„ ,, -biusin 


19 


31 


„ lacustrine coal-measures . . 


20 





., I^dcs in basin of 


()6 


9 


„ veins . . 


(i6 




Rolxjrt Burns lode . . 


()2 


10 


RocliM moiUonnees 


21 


18 


Rocks of Kakanui Series 


30 


11 


., Maniototo Series 


24 


03 


Rock pillars and knobs 


12 


i 


Rocky debris of Kawarau-Clutha glacier 


20 


12,21 


Royal Standard lode 


02 




3 

63,79 


Rutile . . . . . . 75, 70, 77, 78. 


84, 85 






80 
9 


S. 





Q. 



Quartz in Clutha gravels, Cromwell basin 


14 


„ Crystalline . . 


.63,6.5,66 


drifts 


. 31, 41 


„ „ Origin of gold in 


42 


„ gravel 


7 


..grit 


.31,32,40 



I Sands, Drifting, on Cromwell Flat 

Sandstone.. .. 14,15,16,18.21,28,32, 

I ,, in fluvio-glacial drifts facing Arrowtown 

I „ gravels 

! Scheelite . . . . . . . . 29, 

Schist . . . . . . . . 7, 

(See aiso Chlorite-schist, Mica-schist, and 
Maniototo Series.) 

.Schist, Boiob of, at Cromwell 

Schists along fault at Carrick Range . . 



35 

34, 85 
21 
33,42 
56, 63 
33, 34 



42 
11 



92 



Bannookburn 



Schists, Disposition of, on Dimstan Range 

in vicinity of Roaring Meg 
., Pisa fault 

>Liniot:itian, Metamorphism of 

Origin of 

Stratitieation of, at Ida ^'alley, Pisa^'and 
Bannockburn faults 

Tliiikncss of 
,, and Pliocene beds at Anderson's Creek. 
Schistose greywacke 
Scope of the work . . 
Sea, Access of, to Maniototo basin 
Secondary enricliment 
Senecios 
Sericit« 
Sericitic mica 

,, muscovite 
Serjjentine 
Shag Valley 
Shale in lake-beds at 
Shales 

Shelly limestone 
Shepherd's Creek Coal-mine . . 
Shingly Gully, Antimony lodes at 
Silica 
Silver 

Single Cone, Remarkables 
Sluicing, Blowing-dowTi system of 
Smith's Gully : Gold in gravel wash 

,, ,, quartzose drift at 

., ,, schist wash 

Soho Valley 

Some principles of concentration in river-bed 
gravels 

(See also Table of Contents, Chapter iv.) 
Sonora gold- and silver-bearing zone 
South lode. Bendigo 
Specular iron 
Sphene 

Springburn Creek : Asbestos in serpentine dyke 
St. Bathan's Range 
Star of the East lode 
Subaerial erosion 
Syenite 

Sj'stematic investigation of block nunmtains 
Systematic investigation of blcck mountains 
Scheme for the, by Professor W. M. Davis . 



Table cf geological formations 

Table-topped ranges 

Tale 

Tarras terrace 

Te Anau Series 



28, 



81, 



p 


age 
9 


Tectonic movement . . 








11 


Terrace-gravels . . . . . . i 




11 


Tertiary clays and sandstones 




25 


„ coals of New Zealand 


7 


25 


Thermal metamorpliism 
Thickness of Kakanui Series 




10 


„ Maniototo Series . . 


3, 


25 


Thompson's t!reek . . 




9 


Tillman, Mr. William 




78 


Tinkers alluvial workings, Fault-fracture exposed 




2 


at 




7 


Tinkers drifts, Origin of gold in 




64 


Tinselbum 




23 


„ Coal in . . 


78 


80 


Totara [Podocarpus totara) 


76 


84 


Trans]jorted gold 




24 


Travelling drift. Descent and arrest of gold in . . 


29 


79 

7 

17 


Twin fissures 








31 






34 

70 


U. 


67, 


68 


Ulrich, Professor 


56, 


57 
66 
21 
47 






57 


V. 




41 






46 


^'alleys 


. 




20 


,, of erosion 

„ ,, Dunstan Gorge 








36 


,, „ Kawarau Gorge 
Vegetation . . 








57 


Venus, Shells of 






50 


53 
25 


Veronica 
Victoria Flat 






82 


83 
68 


,, moraine 
Vinegar Hill fault-fracture 








19 






61 






8 






34 
13 


w. 







34. 



13 



24 

6, 9 

20. 79 

57 

27 



VVaikerikeri alluvial workings : Fault-fracture 

,, fault 

,, Gorge of 

Waipara Series 
Waitaki Valley 
Wakefield Siu-vey District 
Wanaka watershed . . 
Water-supply 

(See also Artesian water in Central Otago.) 
Western Otago, Dry belt of . . 
Winter Creek 
Work, Scope of the 



Page 
57 
42, 50 
27 
4 
29 
30 
25 
57 
43 

9 
57 
22 
71 
23 
39 
39 
63 



62 



1 

20 

20 

21 

2,23 

34 

23 

21 

21, 33 

9 



9 
10, 13 
9 
7 
7 
1 
22 
2 

2 

66 
2 



By Authority : John Mack.at, Government Printer, Wellington. — 1908. 



[l,.503/9/U7— 9185 



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